function calculateSavings(frm) {
	
	var monthlyPayment = parseInt(frm.monthlyPayment.value);
	var months = frm.months.value;
	var aer = frm.rate.value;
	
    var totalSavings = monthlyPayment;
    var amountSaved = 0;
                     
    for( var i=1; i<=months; i++ ) {
        totalSavings += amountSaved;
        amountSaved = ( (aer / 100) * totalSavings) / 12 + monthlyPayment;
    }
    
    var interestEarned = totalSavings - (monthlyPayment * months);
    var paidIn = monthlyPayment * months;
    
    //build output
    var out = '<strong>After ' + months + ' month' + (months > 1 ? 's' : '') + '...</strong>';
    out += '<ol><li><label>Amount paid in:</label><strong>&pound;' + paidIn.toFixed(2) + '</strong></li>';
    out += '<li><label>Interest earned:</label><strong>&pound;' + interestEarned.toFixed(2) + '</strong></li>';
    out += '<li><label>Total:</label><span>&pound;' + totalSavings.toFixed(2) + '</span></li></ol>';
    
    document.getElementById('savings_calculator_results').innerHTML = out;
}