(ab)² and ab² are not equal. When you have something in parentheses being squared, you have to square everything inside, so in the case of (ab)², you have to "distribute" the ² to both variables inside. That gives you a²b², not just ab².
If the abstract way is kind of confusing for you, just pick two random numbers for a and b and plug them in to test it. Say a = 3 and b = 4. Then
Assuming that the clerk works regular 40 hour per week, then he has worked 6.25 extra (overtime) hours this week. Then his extra pay for overtime work would be:
