Calvin deposits $400 in a savings account that accrues 5% interest compounded monthly. After c years, Calvin has $658.80. Makayla deposits $300 in a different savings account that accrues 6% interest compounded quarterly. After m years, Makayla has $613.04. What is the approximate difference in the number of years that Calvin and Makayla have their money invested?

Use the compound-interest formula A = P(1 + r/n)^(nt). For Calvin, 658.80/400 = 1.647, which at 5% compounded monthly takes about 120 months, or 10 years. For Makayla, 613.04/300 is about 2.043, which at 6% compounded quarterly takes about 48 quarters, or 12 years. Makayla invests her money about 2 years longer, so the correct choice is B.

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