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Which part of a feedback mechanism is able to monitor the conditions outside of cells and usually uses nerve cells to relay this information to an intergrating center

Identify the missing numbers below to show the result of multiplying the numbers (1.6 × 10-19)(5.0 × 106) = c × 10d

An alloy contains 66 g of pure zinc. what is the percentage of zinc in the alloy? express your answer to two significant figures and include the appropriate units.