You invested $$11,000$ in a portfolio with an expected return of $6\mathrm{.}7$ per cent and $$19,000$ in a portfolio with an expected return of $15\mathrm{.}2$ per cent. The expected return of the combined portfolio is $($as a percentage to two decimal places eg $2\mathrm{.}881\%$ is $2\mathrm{.}88))$

a$.12\mathrm{.}08\%$

b$.13\mathrm{.}87\%$

c$.7\mathrm{.}20\%$

d$.11\mathrm{.}32\%$