If Eight Workers Can Manufacture 70 Tables Per Day and Nine

If eight workers can manufacture 70 tables per day and nine workers can manufacture 90 tables per day,

A) the marginal product of hiring the ninth worker is 20 tables
B) the marginal product of hiring the ninth worker is 10 tables
C) the marginal revenue associated with the ninth worker is $90 if nine tables sell for $10 each
D) there are diminishing marginal returns to labor,starting with the ninth worker
E) average revenue is rising