$12.$ Compared to a plain vanilla bond with no embedded options, investors will ask for a to$-$maturity to hold a convertible bond, and ayield$-$yield$-$to$-$maturity to hold a callable bond.$($Assuming all bonds are issued by the same company, with the same coupon rate and maturity$)\mathrm{.}1)$ Lower, lower b$)$Higher$,$ higher c$)$Higher$,$ lower d$)$Lower$,$ higher