public class ConversionTool {

    public static void main(String[] args){
    }

    public static float CentimetersToInches(float centimeters){
        float inch = centimeters * (float) 0.393701;
        if (centimeters < 0){
            return 0;
        } else {
            return inch;
        }

    }

    public static float InchesToCentimeters(float inches){
        float centimeters = inches * (float) 2.54;
        if (inches < 0) {
            return 0;
        } else {
            return centimeters;
        }

    }

    public static float FeetToMeters(float feet){
        float meters = feet * (float) 0.304800164592;
        if (meters < 0){
            return 0;
        }
        return meters;
    }

    public static float MetersToFeet(float meters){
        float feet = meters * (float) 3.28084166666666599;
        if (meters < 0) {
            return 0;
        } 
        return feet;
    }

    public static float CelsiusToFahrenheit(float celsius){
        float fahrenheit =((celsius)* (float)1.8) + (float)32 ;
        if (fahrenheit < 0 ){
            return 0;
        }
        return fahrenheit; //this is the problem
    }

    public static float FahrenheitToCelsius(float fahrenheit){
        float celsius = (fahrenheit - 32)/(float)1.8;
        if (fahrenheit < 0) {
            return  0;
        }
        return celsius; //this is the problem too
    }

    public static float MphToKph(float mph){
        float kph = mph * (float) 1.60934;
        if (mph < 0) {
            return 0;
        }
        return kph;
    }

    public static float KphToMph(float kph){
        float mph = kph *(float) 0.621371;
        if (kph < 0){
            return 0;
        }
        return mph;
    }
}