How to create a faulty calculator in C Programming using If Else?

Code for faulty calculator whose outcomes will be wrong on these conditions and true results for other calculations using IfElse Statement:

55+6=77

56-4=7

45*3=77 and

56/6=4

#include<stdio.h>
#include<conio.h> 
void main()
{
    float a, b, sum, sub, mul, div, inp;
    printf("Enter a Operator you want to use: \n 1. Sum\n, 2. Difference \n 3. Multiplication \n 4. Division \n");
    scanf("%f");
    printf("Enter first number: ");
    scanf("%f", a);
    printf("Enter Second number: ");
    scanf("%f", b);
    sum = a + b;
    sub = a - b;
    mul = a * b;
    div = a / b;
    if (inp == 1)
    {
        if (a == 56 & b == 6)
        {
            printf("Sum is 77");
        }
        else
        {
            printf("Sum is %f", sum);
        }
        if (inp == 2)
        {
            if (a == 56 & b == 6)
            {
                printf("Difference is 7");
            }
            else
            {
                printf("Difference is %f", sub);
            }
        }
        if (inp == 3)
        {
            if (a == 45 & b == 3)
            {
                printf("Product is 77");
            }
            else
            {
                printf("Product is %f", mul);
            }
        }
        if (inp == 4)
        {
            if (a == 56 & b == 6)
            {
                printf("Division is 4");
            }
            else
            {
                printf("Division is %f", div);
            }
        }
        else
        {
            printf("Enter a valid Operator");
        }
    }
    getch();
}