hmm, let's C:twisted:

void userInput (int matrix[R_SIZE][C_SIZE], int row, int col) //gathering user input
{
/*You are using a for loop in main().This function just accepts input for a...

What if '15' does not exist in the array, what happens then ?
How far will index go ?

or, if there are multiple copies of '15'?

Instead of putting the whole thing in main(), why not make one or two different functions for computing the total salary and gross salary.

const int OVERTIME_MULTIPLE = 1.5;
const int...

The series breaks down to::
1 - 2 / (2 *1) +3 / (3*2!) -....
i.e 1 - 1 + 1/2! - 1/3!
So the first (major) 2 terms of the series cancel out.
Now, may be you define a variable
int sign_carrier =...