If f (x) satisfies f (a × b) = f (a) + F (b) (a, B belongs to R) and f (2) = m, f (3) = n, then f (72)=

If f (x) satisfies f (a × b) = f (a) + F (b) (a, B belongs to R) and f (2) = m, f (3) = n, then f (72)=

Because f (2) = m, f (3) = n
So f (6) = f (2 * 3) = f (2) + F (3) = m + n
f(12)=f(3*4)=f(3)+f(4)=f(3)+2f(2)=n+2m
So f (72) = f (6 * 12) = f (6) + F (12) = 2n + 3M