function toggleImg(img)
{
	if (document.getElementById(img + '_on').style.display == 'none')
	{
		document.getElementById(img).style.display = 'none';
		document.getElementById(img + '_on').style.display = 'block';
	}
	else
	{
		document.getElementById(img).style.display = 'block';
		document.getElementById(img + '_on').style.display = 'none';
	}
}

function calculate()
{
	var numMembers = parseInt(document.getElementById('members').value);
	var numGallons = parseInt(document.getElementById('gallons').value);
	var numStorage = parseInt(document.getElementById('storage').value);
	var gallons = (numMembers * numGallons) * numStorage;

	if ((gallons == 0) || (isNaN(gallons)))
	{
		alert("Please enter numbers in all fields");
	}
	else
	{
		if (gallons <= 250)
		{
			tankSize = 250;
			link = 'http://www.surewatertanks.com/cart/index.php?main_page=product_info&cPath=1&products_id=24';
		}
		else if (gallons > 250 & gallons <= 525)
		{
			tankSize = 525;
			link = 'http://www.surewatertanks.com/cart/index.php?main_page=product_info&cPath=1&products_id=25';
		}
		else
		{
			tankSize = 525;
			document.getElementById('total').innerHTML = "" + gallons;
			alert("Please call for information");
		}

		document.getElementById('total').innerHTML = "" + gallons;
		document.getElementById('size').innerHTML = "<a href='" + link + "'>" + tankSize + "</a>";
	}
}