Figure 8.18 shows that the short-run marginal cost curve may lie above the long-run marginal cost curve.

Question:

Figure 8.18 shows that the short-run marginal cost curve may lie above the long-run marginal cost curve. Yet, in the long run, the quantities of all inputs are variable, whereas in the short run, the quantities of just some of the inputs are variable. Given that, why isn't short-run marginal cost less than long-run marginal cost for all output levels?