What will be the output of the following code

#define mul(x,y) (x * y)

int main() {

int x = 3;

int y = 4;

int z = 0;

z = mul(x+1, y+1);

printf(4*5 = %d , z);

}

a) 8

b) 10

c) 12

d) 20

e) none of the above