discountrates = new Array(3)
discountrates[0] = 3.00			
discountrates[1] = 2.50				
discountrates[2] = 2.00 		  
discountrates[3] = 1.50 				


var discountRate;

function CheckNumber(inputField) {

    var str = inputField.value;

    if (str.length == 0) return false;

    for (var i = 0; i < str.length; i++) {
        var ch = str.substring(i, i + 1)
        if (ch < "0" || "9" < ch) return false;
    }

    if (parseFloat(str) < 0) return false;

    inputField.value = str;
    return true;
}

function SetDiscountRate() {

    var appliances = parseFloat(document.getElementById("appliances").value)
    var appliancesNum = 0;
    var discountRateIndex = 0;


    if (appliances <= 50)
        priceRangeIndex = 0;
    else if ((appliances > 50) && (appliances <= 100))
        priceRangeIndex = 1;
    else if ((appliances > 100) && (appliances <= 150))
        priceRangeIndex = 2;
    else if (appliances > 150)
        priceRangeIndex = 3;

    discountRateIndex = (priceRangeIndex * 4) + document.getElementById("discount_rate").selectedIndex;
    discountRate = discountrates[discountRateIndex];

    Calculate();
}

function Calculate() {

    if (parseFloat(document.getElementById("appliances").value) < 0) {
        alert("Please enter a number of appliances of more than 0.")
        return false;
    }

   
    var j;
    var p = 1;
    var iRateMonthly = interestRate / 12;

    for (j = 0; j < numberOfPayments; j++)
        p = p * (1 + iRateMonthly);

    document.getElementById("result").value = parseInt(appliances * discountRate);
}