Solve the problem. A company knows that unit cost C and unit revenue R from the production and sale of x units are related by C = R2/142,000 + 11,329. Find the rate of change of revenue per unit when the cost per unit is changing by $12 and the revenue is $1000. Solution dC/dt=12 2R(dR/dt)/142000=12 dR/dt=12*142000/(2*1000) =852.