Solve the Problem $C D$ the Cost in Dollars to Produce A a New

Multiple Choice

Solve the problem.
-A rock group is producing a new $C D$ . The cost in dollars to produce a $C D$ is given by $C(x, y) =21,500+x^{2}-180 x+3 y^{2}-108 y$ , where $x$ is the number of man hours of work required and $y$ is the number of hours of studio time required. Find the value of $x$ and the value of $y$ that minimize the cost.

A) 89 man hours of work; 14 hours of studio time
B) 90 man hours of work; 18 hours of studio time
C) 92 man hours of work; 15 hours of studio time
D) 95 man hours of work; 20 hours of studio time