The cost of making $x$ units is $C(x) = 2x^{2} + 8x + 200$ rupees. What is the least possible average cost per unit?

Explanation

1. 01

   Average cost $= 2x + 8 + \frac{200}{x}$; its derivative $2 - \frac{200}{x^{2}} = 0$ at $x = 10$.

2. 02

   At $x = 10$: $20 + 8 + 20 = 48$ rupees per unit.