Answer:
In the short run, these workers are VARIABLE inputs, and the ovens are FIXED inputs.
NUMBER OF OUTPUT (PIZZAS) MARGINAL PRODUCT
WORKERS OF LABOR (PIZZAS)
0 0 -
1 100 100
2 180 80
3 240 60
4 280 40
5 300 20
Marginal product of labor is how much does total output change if one additional unit of labor is employed. The formula used to calculate it = total output with n+1 workers minus total output with n workers.