$5.[$Show Calculation$]$ You invest $70\%$ of your money on a stock with expected return of $15\%$ and standard deviation of $22\%.$ The rest of your money is invested in T$-$bills with expected return of $7\%.$ The expected return and standard deviation of your complete portfolio are

a$.12\mathrm{.}6\%$ and $15\mathrm{.}4\%.$

b$.15\%$ and $22\%.$

c$.7\%$ and $0\%.$

d$.11\%$ and $11\%.$

e$.$ None of the above option is correct.