The following function calculates the coupon rate. Please complete the blanks within the function $($bond$\_$value: current bond price, par: par value, ttm: time to maturity, and y: yield$).$

c$\_$rate $<-$ function$($bond$\_$value, par, ttm$,$ y$)\{$

t $<-$ seq$(1,$ ttm$,1)$

pv$\_$factor $<-1/(1+$y$)^$t

$($bond$\_$value $-$ par $/(1+$y$)^$ttm$)/($par$*$sum