Answer:
see below
Explanation:
Putting n=1 into the formulas eliminates the first two choices, since they evaluate to 3.57 and 0.85, respectively, not 4.2.
Putting n=2 into the formula eliminates the third choice, because you know that 4.2(0.15) < 3.57 without even using a calculator.
The only viable choice (and the correct choice) is the last one.