function calculate()
{  


	var cost = document.getElementById("cost").value;
	if ( cost.length == 0 )
	{
		 alert("Please enter the price of a cup of coffee");
		 return;
	}
	cost = fixNumber(cost);
	cost = parseFloat(cost);
	if ( isNaN(cost) )
	{
		 alert("Please enter the price of a cup of coffee as a number");
		 return;
	}
	if ( cost <= 0 )
	{
		 alert("Your coffee is free.");
		 return;
	}
	var deduction = document.getElementById("deduction").value;
	if ( deduction.length == 0 )
	{
		deduction = 0;
	}
	else
	{
		deduction = fixNumber(deduction);
	}
	deduction = parseFloat(deduction);
	if ( isNaN(deduction) )
	{
		 alert("Please enter the price of the cheaper coffee as a number");
		 return;
	}
	if ( deduction>=cost )
	{
		alert("The 'cheaper coffee' is as expensive, or more, than the coffee shop coffee! You won't save any money.");
		return;
	}

	cost = cost - deduction;

	var cpw = document.getElementById("cpw").value;
	if ( cpw.length == 0 )
	{
		 alert("Please enter how many cups you drink per week");
		 return;
	}
	cpw = fixNumber(cpw);
	cpw = parseFloat(cpw);
	if ( isNaN(cpw) )
	{
		 alert("Please enter how many cups a week you drink, as a number.");
		 return;
	}
	if ( cpw <= 0 )
	{
		 alert("You don't drink coffee, and thus don't spend your money in the coffeeshop. Congrats!");
		 return;
	}



	var years = document.getElementById("years").value;
	if ( years.length == 0 )
	{
		 alert("Please enter number of years to calculate.");
		 return;
	}
	years = fixNumber(years);
	years = parseInt(years);
	if ( isNaN(years) )
	{
		 alert("Please enter number of years as a number.");
		 return;
	}
	if ( years <= 0 || years > 100 )
	{
		 alert("Please enter number of years between 1 and 100");
		 return;
	}

	var rate = document.getElementById("rate").value;
	if ( rate.length == 0 )
	{
		 alert("Please enter an interest rate");
		 return;
	}
	rate = fixNumber(rate);
	rate = parseFloat(rate);
	if ( isNaN(rate) )
	{
		 alert("Please enter the interest rate as a number");
		 return;
	}
	if ( rate < 0 )
	{
		alert("Please enter a rate of interest >= 0" );
	}


	var results = "<table cellpadding=\"0\" cellspacing=\"0\" class=\"data\">";
	results += "<tr><th>Year<th>Starting Amount<th>Interest Earned<th>Money Saved This Year<th>Total Saved";
	var i;
	var money = 0;
	for (i=0; i<=years; i++)
	{
		results += "<tr><td>" + i + "<td>" + formatDollars(money);
		var interest = money * (rate / 100);
		results += "<td>" + formatDollars(interest);
		var saved = cpw*52.177457*cost; // 52.2 weeks in a year
		results += "<td>" + formatDollars(saved);
		money = money + interest + saved;
		results += "<td>" + formatDollars(money);
	}

	 
	var x = document.getElementById("results");


	x.innerHTML = results;
	x.style.display = "block";
}