A firm producing consumer electronics operates in perfectly competitive product and labour markets. Which of the following changes would result in a movement along the firm's demand curve for labour, rather than a shift in the curve?
A significant rise in the price of automated assembly machinery that can substitute for manual assembly workers
A legislative increase in the national minimum wage rate that the firm is legally required to pay
A successful nationwide advertising campaign that increases consumer demand for the firm's consumer electronics
An intensive training program that successfully raises the marginal physical productivity of the workforce
