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

r$1=4\mathrm{.}1\%$

r$2=4\mathrm{.}9\%$

r$3=5\mathrm{.}6\%$

r$4=6\mathrm{.}5\%$

What are the following forward rates, where f$1,$k refers to a forward rate for the period beginning in one year and extending for k years?

a$)$ f$1,1=?$

b$)$ f$1,3=?$

$($Note: Express your answer in percentages; round your answer to four decimal places.$)$