Sales for Hanebury Corporation's just-ended year were $10 million. Sales were $5 million 4 years earlier.

At what rate did sales grow? Round your answer to the nearest whole.

Suppose someone calculated the sales growth for Hanebury Corporation in part a as follows: "Sales doubled in 4 years. This represents a growth of 100% in 4 years, so, dividing 100% by 4, we find the growth rate to be 25% per year." Explain what is wrong with this calculation.