Question 60638
C(x) = 0.02x^2 - 3.4x + 150
Differentiating the above with respect to x,
C '(x) = (0.02)(2)x - 3.4 + 0 [because differential of a constant is zero.]-(1)
Equating C '(x) to zero,
==> (0.02)(2)x - 3.4 = 0
==> 0.04x - 3.4 = 0
==> 0.04x = 3.4
==> 0.04x/0.04 = 3.4/0.04
==> x = 85

Now differentiating equation (1) again we get..
C '' (x) = 0.04 which is positive.

So x = 85 units the unit cost is minimum.