Capitalization table with and without full ratchet AD protection

Assume the founders of a company own $12$ million common shares before a first$-$round venture capital financing. In the first round of external financing, Series A preferred shareholders buy $4\mathrm{.}0$ million shares for $$\frac{1\mathrm{.}00}{?}$ share and receive a $25\%$ ownership stake. The company struggles and must sell an additional $3\mathrm{.}0$ million Series B preferred shares for $$0\mathrm{.}50/$share in a second$-$round financing two years later. Calculate:

a$.$ The post$-$money valuation of the investee company after the Series A first$-$round financingn b$.$ The percentage of the company the Series A shareholders will own after the Series B financing if the Series A shares have no antidilution protection. c$.$ The percentage of the company the Series A shareholders will own after Series B financing if the Series A shares have full$-$ratchet antidilution $($AD$)$

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