Consider the following spot interest rates for maturities of one, two, three, and four years.

r$1=6\mathrm{.}3\%$ r$2=6\mathrm{.}7\%$ r$3=7\mathrm{.}4\%$ r$4=8\mathrm{.}2\%$

Assuming a constant real interest rate of $2$ percent, what are the approximate expected inflation rates for the next four years?