The following table summarizes property, plant, and equipment as of April 30, 2021 and 2020 (in thousands):

	April 30, 2021			April 30, 2020
Machinery and equipment	$	15,041		$	12,987
Software and hardware		5,075			4,960
Leasehold improvements		2,273			2,054
		22,389			20,001
Less: Accumulated depreciation and amortization		(13,181	)		(10,854	)
		9,208			9,147
Construction in progress		1,784			530
Total property, plant, and equipment, net	$	10,992		$	9,677

Depreciation expense for the fiscal years ended April 30, 2021, 2020, and 2019 was $3.5 million, $3.4 million, and $2.8 million, respectively.

For the fiscal year ended April 30, 2020, we recorded $2.2 million of leasehold improvements for the office buildout of our Columbia, Missouri facility for which we received a cash incentive from the lessor at the inception of the lease for that facility. We also recorded a corresponding lease incentive liability at the inception of the lease when we received the funds from the lessor. As of April 30, 2020, the lease incentive was recorded as a reduction of right-of-use lease liabilities on our consolidated and combined balance sheet. During fiscal 2020, we finalized a sublease of this facility, and, as a result of this sublease, we recorded a $713,000 impairment of this leasehold improvement.

The following table summarizes depreciation and amortization expense, which includes amortization of intangibles, by line item for the fiscal years ended April 30, 2021, 2020, and 2019 (in thousands):

	For the Years Ended April 30,
	2021		2020		2019
Cost of sales	$	1,016	$	1,837	$	1,969
Research and development		43		83		81
Selling, marketing, and distribution		114		175		39
General and administrative (a)		18,653		21,814		22,901
Total depreciation and amortization	$	19,826	$	23,909	$	24,990