int puzzle$($int start, int end$)$

if $($start $>$ end$)$

return start $-$ end;

else if $($start $==$ end$)$

return start $+$ end;

else

return end $*$ puzzle$($start $+1,$ end $-1)$;

Consider the accompanying definition of a recursive function. What is the output of the following statement? cout $$ puzzle $(3,7)$ endl;

a$.21$

b$.420$

c$.10$

d$.42$