Using the relevant information shown in the picture, what is a potential purchaser's housing expense ratio?

Monthly salary $($husband$)$: $$6,248\mathrm{.}67$

Monthly salary $($wife$)$: $$7,414\mathrm{.}33$

Monthly mortgage payment: $$2,100$

Interest rate: $6\mathrm{.}5\%$

Term of loan: $30$ years

Annual property tax: $$5,500$

Annual property insurance: $$6,500$

Monthly credit card: $$300$

Car payment: $$250$

$($a$)9\%$

$($b$)23\%$

$($c$)25\%$

$($d$)31\%$