21. Again consider the firm whose data are shown in the table to the right. Suppose it must pay its workers $20 per hour and further suppose that fixed costs are zero. If this firm employs exactly 7 workers the output price must fall between:

at least $2.40 but not quite $2.50
at least $4.00 but not quite $5.00
at least $5.00 but not quite $6.67
at least $6.67 but not quite $10.00
at least $20 but not quite $22

Workers	Output
1	10
2	22
3	31
4	40
5	47
6	52
7	56
8	59
9	61
10	62