In my first function "compute" if I want to return the values of "sum" and "sum_of_squares" in main what do I have to do?

Code:

//Name: Joseph Valenzuela
//Date: March 11, 2003
//Purpose: To design and implement my own program for project1.
#include <iostream.h> // For output to the screen and input from user
#include <fstream.h> // To allow input and output streams
#include <stdlib.h> // Contains exit function
#include <math.h> // Contains square root function
double compute();
//Precondition:
//Postcondition:
double mean(double xnum, double sum);
//Precondition:
//Postcondition:
double deviation(double var);
//Precondition:
//Postcondition:
double variance(double sum_of_squares, double xnum, double avg);
//Precondition:
//Postcondition:
void main()
{
double xnum,sum,avg;
ifstream input_data;
cout <<"\nWELCOME TO THE BASIC STATISTICS PACKAGE!\n";
cout << "Enter amount of numbers to be evaluated: ";
cin >> xnum;
sum = compute();
avg = mean(xnum, sum);
cout << sum << endl;
cout << avg << endl;
}
double compute()
{
double sum=0, sum_of_squares=0, in_num=0, count=0;
ifstream input_data;
input_data.open("stats.dat");
if (input_data.fail())
{
cout <<"Input file could not be opened.\n";
exit(1);
}
input_data >> in_num;
while (!input_data.eof())
{
count++;
sum += in_num;
sum_of_squares += in_num*in_num;
input_data >> in_num;
}
return(sum);
return (sum_of_squares);
}
double mean(double xnum, double sum)
{
double avg=0;
avg = sum/xnum;
return(avg);
}
double variance(double sum_of_squares, double xnum, double avg)
{
double var=0;
var = (sum_of_squares/xnum) - (avg*avg);
return(var);
}
double deviation(double var)
{
double dev;
dev = sqrt(var);
return(dev);
}