Assume you make the following$$ investments:

a$.$

You invest a lump sum of $7550$ for $5$ years at $12\%$ interest. What is the$$ investment's value at the end of $$years$?$

b$.$

In a different account earning $12\%$interest$,$ you invest $1510$ at the end of each year for five years. What is the$$ investment's value at the end of $$years$?$

c$.$

What general rule of thumb explains the difference in the$$ investments' future$$ values?