For the following operations, define the worst$-$case runtime complexity in big$-$O notation in terms of n$.$

b$)$

int sum $=0$;

for $($int i $=1$; i $<=$ m; i$++)$

for $($int j $=1$; j $<=$ n; j$*=2)$

for $($int k $=1$; k $<=$ n; k$++)$

sum $+=($i$+$j$)$;

is it O$($log n$*$n$^2),$ O$($log n$*$n$),$ O$($n$),$ or O$($n$^2)$