Hi py0520,

The prompt tells us how an employee's pay is 'modified' depending on the number of hours that are worked each week AND the specific days that are worked. We're asked how much a particular employee was PAID last week. To answer this question, we need to know the employee's base pay rate AND the number of hours worked AND whether any hours were worked on Sunday or not.

1) The employee's regular hourly rate is $10.

This Fact tells us NOTHING about the total hours worked or the days that were worked.
Fact 1 is INSUFFICIENT.

(2) Last week the employee worked a total of 54 hours but did not work
more than 8 hours on any day.

This Fact tells us NOTHING about the employee's base pay nor the days that were worked.
Fact 2 is INSUFFICIENT.

Combined, we know the employee's base pay ($10/hour) and that 54 hours were worked (with no more than 8 hours per day), but the answer to the question changes depending on how those 54 hours are scheduled.

With 54 hours, we could have six 8-hour days and one 6 hour day (or that time could be apportioned differently). In this one example, if the 6-hour day is on a Sunday, then we'll have a different total than if it were on a Monday. As such, the answer to the question changes.
Combined, INSUFFICIENT.

Final Answer: E

GMAT assassins aren't born, they're made,
Rich