Which forward rate cannot be computed from the one$-,$ two$-,$ three$-,$ and four$-$year spot rates?

$($a$)1-$year loan beginning in two years $(f_{2,1})$

$($b$)2-$year loan beginning in two years $(f_{2,2})$

$($c$)3-$year loan beginning in two years $(f_{2,3})$

$($d$)1-$year loan beginning in one year $(f_{1,1})$