Function pointer and pointer sizes

Just a simple mathematical problem.....of perform the basic functions using function pointers, and also passing functions in void* as a parameter....

#include <stdio.h>
int add(int a,int b);
int sub(int a, void * b);
int mul(int a,int b);
int div(int a,int b);
int operation(int a,int b,int (*function)(int,int));


int main (int argc, const char * argv[])
{
    //Every of this address is of 8 bytes
  
    printf("%lu\n",sizeof(int *));
    printf("%lu\n",sizeof(float *));
    printf("%lu\n",sizeof(void *));
    printf("%lu\n",sizeof(&add));
  
    
 
    int (*addptr)(int,int);//create a function pointer for add
  
    addptr = &add; //though & is not necessary since its points to the address
  
  
      printf("%lu\n",sizeof(addptr));
  
  
    printf("addittion%d\n",(addptr)(2,3));
  
    int (*subptr)(int,void *);//create a function pointer for sub
  
    subptr =&sub;
  
     printf("subtract%d\n",(subptr)(5,(void *)3));//Pass an object of anytype
  
  
    printf("mutliply->%d\n",operation(2,3,mul));//passing the base address of the method to call
  
    printf("division->%d\n",operation(6,2,div));  
  
    return 0;
}
int operation (int a, int b, int (*functocall)(int,int))
{
  
    return (*functocall)(a,b);
  
}
int div(int a,int b)
{
    return (a/b);
}
int mul(int a,int b)
{
    return (a*b);
}
int add(int a,int b)
{
    return (a+b);
}
int sub(int a,void *b)//resultant is void so can send data of any type
{
    return (a-(int)b);
}