function calculateCost(empty){
			var days = document.calculator.days.value;
			var cats = document.calculator.number.value;
			var sharing = 0;
			var cost = 0;
			var price = 0.00;
			
			if(document.calculator.sharing[0].checked) {
				sharing = 1;
				switch (true){
					case cats == 1:
						price = 6.00;
					break;
					case cats == 2:
						price = 5.50;
					break;
					case cats == 3:
						price = 4.75;
					break;
					case cats > 3:
						price = 4.25;
					break;
				}
			} else {
				sharing = cats;
				price = 6.00;
			}
			ttc = price * cats;
			cost = days * ttc;
			totalcost = cost.toFixed(2);
			document.getElementById('total_price').innerHTML = "£ " + totalcost;
		}