var repayment_amount;
	var interestonly_amount;
	function calculate(){
		$('#howmuch').hide();
		
		var d = document.mortgage_calculator;
		var errors = "";
		var years = d.term.options[d.term.selectedIndex].value;
		
		var debts = stripCurrency(d.debts.value);
		if(isNaN(debts)){
			errors += "Please check that your debt amount is a number\n";
		}else if(debts == ""){
			debts = 0;
		}
		/*
		var monthly_spend = stripCurrency(d.monthly_spend.value);
		if(isNaN(monthly_spend)){
			errors += "Please check that your monthly expenditure is a number\n";
		}else if(monthly_spend == ""){
			monthly_spend = 0;
		}
		*/
		var rate = d.interest_rate.value;
		if(isNaN(rate) || rate == ""){
			errors += "Please enter a rate of interest\n";
		}
		
		var income1 = stripCurrency(d.income1.value);
		var income2 = stripCurrency(d.income2.value);
		if(isNaN(income1) || isNaN(income2)){
			errors += "Please enter correct number\n";
		}else if(income2 == ""){
			income2 = 0;
		}
		
		if(errors){
			alert(errors);
		}else{
			totalincome = parseInt(income1) + parseInt(income2);
			// find dtir %
			if(totalincome >= 10000 && totalincome < 12000){
				dtir = 0.1;
			}else if (totalincome >= 12000 && totalincome < 15000){
				dtir = 0.25;
			}else if (totalincome >= 15000 && totalincome < 20000){
				dtir = 0.4;
			}else if (totalincome >= 20000){
				dtir = 0.5;
			}else{
			 	dtir = 0;
			}

			max_monthly_payment = ((totalincome/12)*dtir) - debts;
			
			// split formulas out
			n = 1+(rate/1200);
			x = -years*12;
			repayment_amount = (max_monthly_payment*12) * (1200 * (1 - Math.pow(n,x)))/12/rate;
			//interestonly_amount = (Math.pow((rate+1),((years*12)-1))*monthly_spend)/(Math.pow((rate+1),(years*12)))/rate;
			interestonly_amount = max_monthly_payment*12/rate*100;
			
			// do not allow negative amounts:
			if(repayment_amount < 0){repayment_amount = 0;}
			if(interestonly_amount < 0){interestonly_amount = 0;}
			
			// set outputs:

			$('#howmuch').show('slow');
			
			
			d.loanamount_repayment.value = "£"+formatCurrency(repayment_amount);
			d.loanamount_interestonly.value = "£"+formatCurrency(interestonly_amount);
			Set_Cookie("ahloanamt",formatCurrency(repayment_amount),expires,'/');
		}
	}