Assuming all firms have identical cost functions. Now suppose there is an increasing shift in the demand curve. As we all know that for increasing costs case, both average costs (AC) and marginal costs (MC) faced by a typical firm would be higher. The question is, whether the optimal production level of a typical firm remains constant or increases (or decreases! is it possible?) as compared to previous long-run equilibrium position?
In other words, as both MC and AC curve will shift upward, can one predict with certainty the direction in which optimal production level moves to ensure MC=AC_min?