$2.$ The following pattern for one$-$year Treasury bills is expected over the next four years:

Year $1$: $5\%$

Year $2$: $6\%$

Year $3$: $7\%$

Year $4$: $8\%$

a$.$ What return would be necessary to induce an investor to buy a

i$.$ two$-$year security

ii$.$ three$-$year security

iii. four$-$year security

b$.$ Graph the term structure of interest rates for years $1$ through $4$