in C please

Write a function that returns as a double-precision number the average of elements from index to index inclusively, assuming indices and are in range. The function has the following inputs, in this order: - an array of integers - an integer number of elements - an integer - an integer Sample Test Case You may optionally write a function so that you can perform appropriate tests on the function. It's up to you to decide what code you write in to perform the testing - but you should consider more test cases other than the sample test case given above. Any code you write must also use good programming style, as discussed below