Quantity demanded	Price
0	75
5	70
10	65
15	60
20	55
25	50
30	45
35	40
40	35
45	30
50	25

Quantity produced	Total cost
0	275
5	400
10	475
15	525
20	575
25	650
30	750
35	875
40	1025
45	1200
50	1400

Assuming that this firm is a monopoly, find the optimal quantity to produce.