C++ :: Input Length / Width And Height For 3 Boxes - Sum And Average Volume

How would I make it so that I can have someone input the length, width and height for all 3 boxes and then have it output the sum and average volume? Here's an example of what I would like:

INPUT - Enter Box 1 (Length, Width, Height): 10.1 11.2 3.3
INPUT – Enter Box 2 (Length, Width, Height): 5.5 6.6 7.7
INPUT – Enter Box 3 (Length, Width, Height): 4.0 5.0 8.0
OUTPUT – The sum of the volume is 812.806
OUTPUT – The average volume is 270.935

Here's my original code:

#include <iostream>
using namespace std;
double box(double length, double width, double height); // use double data
int main() {
double sum;
sum = box(10.1, 11.2, 3.3) + box(5.5, 6.6, 7.7) + box(4.0, 5.0, 8.0);

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