General - Always ouputs zero... but that is never the required answer???

#include <iostream>
#include <iomanip>

using namespace std;
double distanceInMiles, variableShippingCost, FixedShipmentCost;

void calculateVariableCost()
{
int firstTierCost, secondTierCost, thirdTierCost;

firstTierCost = 5;
secondTierCost = 4;
thirdTierCost = 3;

if (distanceInMiles < 0)
{
cout << "ERROR: The distance should be a positive value.";
}
if (distanceInMiles >= 0) (distanceInMiles <= 100);
{
variableShippingCost = firstTierCost*distanceInMiles;
}
if (distanceInMiles > 100) (distanceInMiles <=500);
{
variableShippingCost = (100 * 5) + ((distanceInMiles - 100)*secondTierCost);
}
if (distanceInMiles > 500)
{
variableShippingCost = (100 * 5) + ((distanceInMiles - 100)*4) + ((distanceInMiles - 500)*thirdTierCost);
}
}

int main()
{
cout << "Enter the distance in miles: ";
cin >> distanceInMiles;
calculateVariableCost;
cout << "The cost of shipment over ";
cout << distanceInMiles;
cout << " miles is ";
cout<< variableShippingCost;
cout << "\n";
}

Whne you call a functon, use ().


calculateVariableCost();

--------------------------------------