Cthe functions that are called in the main() function to produce these outputs. enter the monthly sales: 14550.00 enter the amount of advanced pay, or enter 0 if no advanced pay was given advanced pay: 100 requirements for the function - determine_comm_rate() sales less than 1.00 rate: .10 sales from 1.00 to 14999.99 rate: .12 sales from 15000.00 to 17999.99 rate: .14 sales from 18000.00 to 21999.99 rate: .16 sales greater than 21999.99 rate: .18

Following are the program in the C programming Language:

#include <stdio.h>  //header file  

//set function for sales

int get_sales(){

int sale;

//print message

printf("Enters monthly sale: ");

scanf("%d",&sale);

return sale;

}

//set function for the advance payment

int get_advanced_pay(){

int advance;

//print message

printf("Enter the amount of advanced pay or enter 0 if no advanced pay was given: ");

scanf("%d",&advance);

return advance;

}

//set fucntion of comman rates

float determine_comm_rate(int sale){

  if(sale<10000)

      return 0.1;

  if(sale<15000)

      return 0.12;

  if(sale<18000)

      return 0.14;

  if(sale<22000)

      return 0.16;

  else

      return 0.18;

}

//set the main function

int main(){

int sale,advanced;

float comm_rate,pay;

sale=get_sales();

advanced=get_advanced_pay();

comm_rate=determine_comm_rate(sale);

pay=sale*comm_rate-advanced;

printf("The pay is %f\n",pay);

if(pay<0)

//if the pay is less than 0

printf("The salesperson must reimburse the company");

}

Output:

Enters monthly sale: 45000

Enter the amount of advanced pay or enter 0 if no advanced paywas given: 1000

The pay is 7100.000488

Explanation:

Here, we set the integer type function "get_sales()" in which we get the monthly sale of the person and then return sales.

Finally, we set the main method in which we call both the functions and print the following output.