Consider the following information for Johnny Manziel's $3-$stock portfolio. If the retum on the market is currently $12\mathrm{.}2$ percent, the nominal risk$-$free rate is $1\mathrm{.}9$ percent, and the required rate of return for this portfolio is $21\mathrm{.}25$ percent, what is the beta for Stock Y$?$

a$.-\mathrm{.}77$

b$.\mathrm{.}81$

c$.\mathrm{.}73$

d$.-\mathrm{.}68$

e$.64$