Assume that the Pure Expectation Theory determines interest rates in the markets. Today's market rates for different maturities follow an interesting pattern. The spot rate for investing for 1 year is 3%. After that, the rate increases by 1% for each year. So, in general, the rate for year Y is simply 3% + 1%*(Y-1).

Given this information, what is the implied interest rate to invest for 1 year, starting in 3 years?

Ans: 9

Why?