Answer:
$2
Step-by-step explanation:
Average total cost is the total cost of production, both variable and fixed cost divided by the no of units produced.
When hired worker = 4 ,
Production = 50 units.
Fixed cost of production = $4
Variable cost of production = $20 ( note that the only variable input is labor)
Marginal product for the 5th labor =2 ( total unit becomes 52)
Average total cost =
(5 *20) + 4 /52 =2