public static string compoundInterest(double p, double r, double n)
 {
     return(Maths.multiply(p, Math.Pow(1 + r, n)).ToString());
 }
        public static string simpleInterest(double p, double r, double n)
        {
            double temp = multiply(p, r);

            return(Maths.multiply(temp, n).ToString());
        }