Given the underneath fragment code that is written in C language, Write down the function with domain and codomain then prove that function is injective (One to one) but it's not surjective (Onto)? SHOW ALL YOUR WORKS, a counterexample is NOT ENOUGH, you have to disprove surjectivity and prove injective.

void fun(unsigned int *m,unsigned int *n ){

unsigned int *z = *m;

*m=3*(*m) - 4* (*n);

*n=2*(*z) + (*n);

}