I can't seem to figure this quadratic -

An aircraft factory manufactures airplane engines. The unit cost C (the cost in dollars to make each airplane engine) depends on the number of engines made. If x
engines are made, then the unit cost is given by the function

C(x) = 0.2x^2 - 48x + 21,748

What is the minimum unit cost?

Do not round your answer.

Please help

1 answer

When x= 120
y =18868. ( That is the minimum point in this quadratic, aka vertex.)