Your firm has a Debt$/$Equity ratio of $($corresponding to debt$/$Total capital of $20\%),$ Beta of $1\mathrm{.}45,$ Risk free: $1\%,$ Equity RP: $6\%,$ tax rate: $30\%.$ Interest expense rate: $2\mathrm{.}75\%.$ You are looking into whether putting more debt on your balance$-$sheets will reduce your WACC of $8\mathrm{.}15\%.$ A banker has run a simulation according to which if the Debt$/$Equity ratio moves to $1/3($corresponding to a debt$/$Total capital of $25\%),$ the WACC of the firm will be $8\mathrm{.}17\%,$ assuming that the interest expense rate will be $3\mathrm{.}25\%.$ This finding contradicts your intuition. You decided to do the calculation again. You found:

A$.7\mathrm{.}5\%$

B$.$ The same WACC as the banker

C$.8\mathrm{.}2\%$

D$.7\mathrm{.}8\%$