The Demand Equation for a Certain Brand of Metal Alloy

Multiple Choice

The demand equation for a certain brand of metal alloy audiocassette tape is , where x represents the number (in thousands) of ten-packs demanded each week when the unit price is $p. ​
How fast is the quantity demanded increasing when the unit price/ten-pack is $20 and the selling price is dropping at the rate of $.11/ten-pack/week? Round your answer to the nearest integer.
Hint: To find the value of x when p = 20, solve the equation for x when p = 20.

A) Increasing at the rate of 93 ten packs/wk.
B) Increasing at the rate of 82 ten packs/wk.
C) Increasing at the rate of 66 ten packs/wk.
D) Increasing at the rate of 31 ten packs/wk.

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