Answer the following questions from (a) through (d):

(a) If TVC = $80 and AVC = 4, then what does quantity (Q) equal?

(b) If the total cost is $40 when Q = 2 and the total cost is $45 when Q = 3, then what does marginal cost equal?

(c) What does average fixed cost equal at Q = 2 if the total variable cost is $15 at Q = 2?

(d) Why does the AFC curve get continually closer to the horizontal X-axis as the quantity of output increases?

Price = $20, quantity = 400 units, unit cost = $15, implicit costs = $4,000. What does economic profit equal?