A firm conducting an IPO of common stock sold $12$ million new shares in the offering at an offer price of $$27$ per share. After the offering, the firm had $7$ million shares outstanding, and the price of those shares in the secondary market was $$32.$ The firm's IPO was underpriced by $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.$

$-20\mathrm{.}60\%$

$12\mathrm{.}75\%$

$18\mathrm{.}52\%$

$15\mathrm{.}63\%$