Two risky portfolios exist for investing: one is a bond portfolio with a beta of $0\mathrm{.}7$ and an expected return of $9\%,$ and another is an equity portfolio with a beta of $1\mathrm{.}5$ and an expected return of $17\%.$ If these portfolios are the only two available assets for investing, what percentage should be invested in bonds if Elaine's desired expected return is $13\%?$