how do I find the minimum cost?

Question

A medical equipment industry manufactures X-ray machines. The unit cost C

 (the cost in dollars to make each X-ray machine) depends on the number of machines made. If x

 machines are made, then the unit cost is given by the function =Cx+−0.3x2150x37,270

. What is the minimum unit cost?

Answer 1

Are the x's an amount or a multiplication sign?