linguistic:paraphrasing, stylistic:tone
Cost functions and relationship to average cost

Here MPL is the ratio of increase in the quantity produced per unit increase in labour: i.e. ΔQ/ΔL, the marginal product of labor. The last equality holds because Δ L Δ Q {\displaystyle {\frac {\Delta L}{\Delta Q}}} is the change in quantity of labor that brings about a one-unit change in output. Since the wage rate is assumed constant, marginal cost and marginal product of labor have an inverse relationship — if the marginal product of labor is decreasing (or, increasing), then marginal cost is increasing (decreasing), and AVC = VC/Q=wL/Q = w/(Q/L) = w/AP