How is marginal cost related to marginal product?

Donny Saltlife shapes surfboards in Hawaii. He leases two production machines, paying \$300 each per week. He cannot increase the number of machines he leases in his contract. He can hire as many workers as he wants at a cost of \$400 per week. These are his only two inputs to produce surfboards. Fill in the remaining columns in the table below.

A firm that sells headphones has the following average total cost schedule:The company currently produces and sells 600 units. A desperate customer calls and offers \$550 for a pair of headphones. Should the company accept the offer?