Can anyone explain me why this code snippet returning 60?

Question

#include <stdio.h>
int f(int n, int m){
static int i=10;
i*=m+n;
if(i>40){
return i;
}
else{
return f(m+n,m-n);
}
}
int main() {
printf("%d",f(2,1));
return 0;
}

Answer 1

f(2,1) //i=10 before this call
= f(3,-1) //i is 30 before this call (10*3)
= 60 //as i becomes 60 in next call f(2,-4), (30*2)

Answer 2

f(2,1) //n=2, m=1
= f(1+2,1-2) //n=3, m=-1

Answer 3

Gaurav Agrawal ohkay got it thanks

Answer 4

Gaurav Agrawal how on second function call f(3,-1) isn't it f(3,1)