function calc(f) {
	amt = f.amt.value;
	annual_int = f.interest.value/100;
	term = f.term.value;
	weekly = annual_int/52;
	fortnightly = annual_int/26;
	monthly = annual_int/12;
	weekly_pay = Math.floor((amt*weekly)/(1-Math.pow((1+weekly),(-1*term*52)))*100)/100;
	fortnightly_pay = Math.floor((amt*fortnightly)/(1-Math.pow((1+fortnightly),(-1*term*26)))*100)/100;
	monthly_pay = Math.floor((amt*monthly)/(1-Math.pow((1+monthly),(-1*term*12)))*100)/100;
	f.weekly.value = currency(weekly_pay);
	f.fortnightly.value = currency(fortnightly_pay);
	f.monthly.value = currency(monthly_pay);
}

function currency(num) {
	var dollars = Math.floor(num);
	for (var i = 0; i < num.length; i++) {
		if (num.charAt(i) == ".")
		break;
	}
	var cents = "" + Math.round(num * 100);
	cents = cents.substring(cents.length-2, cents.length);
	return (dollars + "." + cents)
}