Notice of Filing and Immediate Effectiveness of Proposed Rule Change (1) to Reflect a Change to the Value Used by the iShares Silver Trust, ETFS Silver Trust, ETFS White Metals Basket Trust and ETFS Precious Metals Basket Trust With Respect to Calculation of the Net Asset Value of Shares of Each Trust; and (2) to Reflect a Change to the Underlying Benchmark for ProShares Ultra Silver and ProShares UltraShort Silver