For sequential reaction :

$\begin{array}{l}\mathrm{A}⟶\mathrm{B}+\mathrm{C} ...\left(\mathrm{i}\right)\\ 2\mathrm{B}⟶\mathrm{C}+2\mathrm{D} ...\left(\mathrm{ii}\right)\end{array}$

If $\%$ yield of (i) and (ii) reactions are $90\%$ and $80\%$ respectively, then the overall % yield is expected be: