EXHIBIT 8.4

CUSIP No. 003687209

AGREEMENT CONCERNING JOINT FILING
OF SCHEDULE 13D

The undersigned agree as follows:

(i)            each of them is individually eligible to use the Schedule 13D/A to which this Exhibit is attached, and such Schedule 13D/A is filed on behalf of each of them; and

(ii)            each of them is responsible for the timely filing of such Schedule 13D/A and any amendments thereto, and for the completeness and accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other person making the filing, unless such person knows or has reason to believe that such information is inaccurate.

This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original, but all of which, taken together, shall constitute one and the same instrument.

Dated: July 7, 2022

V. PREM WATSA /s/ V. Prem Watsa THE SECOND 810 HOLDCO LTD.
By:	/s/ V. Prem Watsa
	Name:	V. Prem Watsa
	Title:	President
THE SECOND 1109 HOLDCO LTD.
By:	/s/ V. Prem Watsa
	Name:	V. Prem Watsa
	Title:	President
THE SIXTY TWO INVESTMENT COMPANY LIMITED
By:	/s/ V. Prem Watsa
	Name:	V. Prem Watsa
	Title:	President

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12002574 CANADA INC.
By:	/s/ V. Prem Watsa
	Name:	V. Prem Watsa
	Title:	President
FFHL GROUP LTD.
By:	/s/ V. Prem Watsa
	Name:	V. Prem Watsa
	Title:	President
FAIRFAX (BARBADOS) INTERNATIONAL CORP.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
TIG INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
THE NORTH RIVER INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
UNITED STATES FIRE INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D

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CRUM & FORSTER HOLDINGS CORP.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
FEDERATED INSURANCE COMPANY OF CANADA
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
WENTWORTH INSURANCE COMPANY LTD.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
NORTHBRIDGE GENERAL INSURANCE CORPORATION
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
FAIRFAX FINANCIAL HOLDINGS LIMITED
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	President and Chief Operating Officer
FAIRFAX (US) INC.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D

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CRC REINSURANCE LIMITED
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ALLIED WORLD ASSURANCE COMPANY HOLDINGS, LTD
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ALLIED WORLD ASSURANCE COMPANY HOLDINGS I, LTD
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ALLIED WORLD ASSURANCE COMPANY, LTD
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ALLIED WORLD ASSURANCE HOLDINGS (IRELAND) LTD
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D

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ALLIED WORLD ASSURANCE HOLDINGS (U.S.) LTD
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D

ALLIED WORLD INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
AW UNDERWRITERS INC.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
1102952 B.C. UNLIMITED LIABILITY COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ALLIED WORLD SPECIALTY INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D

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NORTHBRIDGE FINANCIAL CORPORATION
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ZENITH INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
VERASSURE INSURANCE COMPANY
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
ZENITH NATIONAL INSURANCE CORP.
By:	/s/ Peter Clarke
	Name:	Peter Clarke
	Title:	Attorney-in-Fact pursuant to Power of Attorney attached to this Schedule 13D
BRIT REINSURANCE (BERMUDA) LIMITED
By:	/s/ Gavin Wilkinson
	Name:	Gavin Wilkinson
	Title:	Group Chief Financial Officer
BRIT LIMITED
By:	/s/ Gavin Wilkinson
	Name:	Gavin Wilkinson
	Title:	Group Chief Financial Officer

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BRIT INSURANCE HOLDINGS LIMITED
By:	/s/ Gavin Wilkinson
	Name:	Gavin Wilkinson
	Title:	Group Chief Financial Officer