double CalculateChange (double billAmount, double creditAvailable);\ (1) Function definition\ Inside the function compare the creditAvailable to the billAmount:\ if the creditAvailable is less than the billAmount, tell the user they cannot pay the bill and return the original creditAvailable\ if the creditAvailable is greater than or equal to the billAmount, subtract the billAmount from the creditAvailable and return the updated creditAvailable.\ \ (2) Write the main function with the function call. Be sure to declare variables and assign values as needed.