B. 0
Explanation: at sea level is 0, below sea level would be a negative such as -2, and above sea level is any number above zero, such as 2.
Let's use x to represent the number of hours since we don't know that.
750+250x<u><</u><u />2500
Subtract 750 from both sides.
250x<u><</u><u />1750
Divide both sides by 250.
x<u><</u><u />7
The most hours that they can do is 7, or it can be less.
