public double IntegralMonteCarlo(double a, double b, double c, double d, int n)
{
double x, y;
double result = 0.0;
RandomMonteCarlo rand = new RandomMonteCarlo();
for (int i = 0; i < n; i++)
{
x = rand.Next();
y = rand.Next();
result += (b - a) * (d - c) * f(a + (b - a) * x, c + (d - c) * y);
}
return (result / n);
}