Answer:
Here h represents the number of hours he must work in a month.
Since, earning for an hour = $ 25,
⇒ Total revenue for h hours = 25h,
Now, Expenses for a month = $750 for overhead + $110 for phone and fax + $75 for materials
= $ 935
We know that,
Profit = Total revenue - Total expenses
= 25h - 935
a. For the profit more than $ 625,
25h - 935 ≥ 625
Which is the required inequality,
b. 25h - 935 + 935 ≥ 625 + 935
⇒ 25h ≥ 1560
⇒ h ≥ 62.4
Hence, he should work at least 62.4 hours to earn a profit of at least $625.