Suppose flora bakery is the monopolist in the market for banana bread. It’s fixed cost is 3 million. While it’s labour cost and ingredients for producing each pound of banana bread are $60 and $40 respectively. Consumer are unwilling and unable to buy any banana bread when the price is $300 or above, however, the quantity demanded increases by 1000 pounds for each dollar the price drops.

Question

Suppose flora bakery is the monopolist in the market for banana bread. It’s fixed cost is 3 million. While it’s labour cost and ingredients for producing each pound of banana bread are $60 and $40 respectively. Consumer are unwilling and unable to buy any banana bread when the price is $300 or above, however, the quantity demanded increases by 1000 pounds for each dollar the price drops.
How to calculate the marginal cost, average total cost?