Answer:
void getSpeed(int& speed) Â
//the function with reference parameter speed and & denote a reference
{ Â //prompts user to enter a number
 cout << "Enter a number in the range of 20 through 70: ";
 cin >> speed;  //reads the value entered by user
 if(speed < 20 || speed> 70) Â
// if value of speed entered by user is outside the given range
 {
  speed = 0;  // speed is set to 0
 } }
Explanation:
In order to check how this function works you can write a main function and print the value of speed as following:
int main()
{ int speed;
  getSpeed(speed); //calls getSpeed function
  cout<<"speed is "<<speed; } //displays value of speed
Output:
Enter a number in the range of 20 through 70: 50
speed is 50
Output for if condition:
Enter a number in the range of 20 through 70: 80
speed is 0