#include "car.h"
#include <math.h>

double value(double purchasePrice, double milesDriven) {
  double lossFactor;
  lossFactor = log(20)/100000;
  return purchasePrice * exp(-lossFactor * milesDriven);
}

double mileage(double miles, double gallons) {
  return miles/gallons;
}

double averageDepreciationPerMile(double purchasePrice,
                                  double milesDriven)  {
  return (value(purchasePrice, 0) -
          value(purchasePrice, milesDriven)) / milesDriven;
}