Please explain how to calculate marginal product of labor

Question

1a. Joy, who has an income of $40, can spend her income on 2 different goods, smoothies and energy bars. Energy bars cost $2 each, and smoothies cost $4 each. Draw her budget line. 1 

1b. Can she buy 10 energy bars and 5 smoothies? Why or why not? 1

Please explain how to calculate marginal product of labor, fixed cost, variable cost, total cost, and marginal cost for the following example

Marty produces frozen yogurt using fixed and variable inputs. P_labour = $80 per unit per day. Fixed cost = $100 per day

Quantity of Labor Quantity of frozen yogurt

0 0

1 110

2 200

3 270

4 300

5 320

6 330

1. Fill in the marginal product column in the table. Why does marginal product decline as the number of workers increases? 
2. What is Marty's variable cost and total cost when he produces 110 cups of yogurt? 200 cups? Calculate variable cost and total cost for every level of output. Do the same for marginal cost.