Question

A manufacturer has determined that the demand for a certain product is given by the function
p(x)=600-2x, 0 <(or equal) x >(or equal to) 300, where p is the price per unit and x is the number of units sold in a week. Find the rate at which revenue is changing with respects to time when the weekly sales are 120 units if the number of items sold is decreasing by 6 units per week. Recall that revenue R(x)=x(p(x))