Moderate# One Input, Profit Maximization Equation

MICRO-STRH5J

Given production function $y=f(L)$, where $y$ is the amount of output and $L$ is the amount of labor input. With price $p$ and labor wage $w$, which of the following represents the profit-maximizing equation for a firm?

Let $f'(L)$ mean the derivative of the production function with respect to $L$.