Giambona Corporation's stock had a required return of $8\mathrm{.}50\%$ last year when the risk$-$free rate was $2\mathrm{.}50\%$ and the market risk premium was $4\mathrm{.}00\%.$ Then an increase in investor risk aversion caused the market risk premium to rise by $1\%$ from $4\mathrm{.}00\%$ to $5\mathrm{.}00\%.$ The risk$-$free rate and the firm's beta remain unchanged. What is the company's new required rate of return?

a$.9\mathrm{.}00\%$

b$.9\mathrm{.}50\%$

c$.10\mathrm{.}00\%$

d$.10\mathrm{.}30\%$

e$.10\mathrm{.}80\%$