Imagine that a firm produces good X with just two factors: capital, which is fixed in supply; an labour, which is variable. The effect on total output (TPP) of increasing the number of workers is shown in column (2) of the table below. (We will fill in columns (3) and (4) later.) The relationship between the output (total physical product) of good X and the number of workers employed (1) (2) (3) (4) No. of workers TPP APP MPP O 0 1 10 N 26 41 4 52 60 65 67 67 9 63