function CalculateSum(form)
{
var roofarea = parseFloat(form.input_roofarea.value);
var rainfall = 50;

 Item = form.list_regions.selectedIndex;
 Result = form.list_regions.options[Item].text;

 if(Result == "S.Ireland"){
 	rainfall = 1600;
 }
 if(Result == "SE.Ireland"){
	rainfall = 1100;	
 }
 if(Result == "W.Ireland"){
 	rainfall = 1500;
 }
 if(Result == "Mid.Ireland"){
 	rainfall = 900;
 }
 if(Result == "MW.Ireland"){
 	rainfall = 1100;
 }
 if(Result == "NE.Ireland"){
 	rainfall = 900;
 }
 if(Result == "N.Ireland"){
 	rainfall = 1100;
 }
 if(Result == "NW.Ireland"){
 	rainfall = 2000;
 }
 if(Result == "England"){
	rainfall = 850;
 }
 if(Result == "N.England"){
	rainfall = 1020;
 }
 if(Result == "S.England"){
	rainfall = 760;
 }
 if(Result == "Mid.England"){
	rainfall = 600;
 }
 if(Result == "Wales"){
	rainfall = 1420;
 }
 if(Result == "England NW & Wales N"){
	rainfall = 1400;
 }
 if(Result == "England SW & Wales S"){
	rainfall = 630;
 }
 if(Result == "Scotland"){
	rainfall = 1650;
 }
 if(Result == "N.Scotland"){
	rainfall = 1820;
 }
 if(Result == "E.Scotland"){
	rainfall = 1170;
 }
 if(Result == "W.Scotland"){
	rainfall = 1940;
 } 


var yieldPerYear = roofarea * rainfall * 0.85 * 0.9;

var gardening = parseFloat(form.input_gardening.value);
var washmachine = parseFloat(form.input_washmachine.value);
var toilet = parseFloat(form.input_toilet.value);
var other = parseFloat(form.input_other.value);



var dayDemand = gardening + washmachine + toilet + other;
var yearDemand = dayDemand * 365;



var fivePercentAnnualYield = yieldPerYear * 0.05;

var fivePercentAnnualDemand = yearDemand * 0.05;

var result = Math.min(fivePercentAnnualYield, fivePercentAnnualDemand);


form.demand.value = yearDemand;
form.yield.value = yieldPerYear;
form.capacity.value = result;

}

/* ClearForm: this function has 1 argument: form.
   It clears the input and answer fields on the form. 
   It needs to know the names of the INPUT elements in order
   to do this. */

function ClearForm(form)
{
form.input_roofarea.value = "";
form.input_gardening.value = "";
form.input_toilet.value= "";
form.input_washmachine.value = "";
form.input_other.value = "";


form.demand.value = "";
form.yield.value = "";
form.capacity.value = "";
}