function computeCost(){
   if(!isNaN(parseInt(document.getElementById("comic_quantity").value))){
      document.getElementById("comic_quantity").value = parseInt(document.getElementById("comic_quantity").value);
   }else{
      document.getElementById("comic_quantity").value = "1";
   }
   
   if(document.getElementById("comic_quantity").value < 5){
      document.getElementById("comic_quantity").value = "5";
   }
   
   var quantity = parseInt(document.getElementById("comic_quantity").value);
   if(quantity < 20){
      document.getElementById("cost").value = "$" + roundNumber(quantity, 3);
   }else{
      document.getElementById("cost").value = "$" + roundNumber(quantity*0.7, 4);
   }
}

function roundNumber(rnum, rlength) { 
   // Arguments: number to round, number of decimal places
  var newnumber = Math.round(rnum*Math.pow(10,rlength))/Math.pow(10,rlength);
  return newnumber;
}

function generateField(){
   if(document.getElementById("occupation").selectedIndex == 0){
      document.getElementById("replaceme").innerHTML = "";
      document.getElementById("further_info").style.display = "none";
   }else if(document.getElementById("occupation").selectedIndex == 1){
      document.getElementById("replaceme").innerHTML="<label for=\"further_info\">What school do you attend? </label>";
      document.getElementById("further_info").style.display = "block";
   }else if(document.getElementById("occupation").selectedIndex == 2){
      document.getElementById("replaceme").innerHTML="<label for=\"further_info\">What church do you work for? </label>";
      document.getElementById("further_info").style.display = "block";
   }else if(document.getElementById("occupation").selectedIndex == 3){
      document.getElementById("replaceme").innerHTML="<label for=\"further_info\">Which school do work at? </label>";
      document.getElementById("further_info").style.display = "block";
   }else if(document.getElementById("occupation").selectedIndex == 4){
      document.getElementById("replaceme").innerHTML="<label for=\"further_info\">Please enter your occupation: </label>";
      document.getElementById("further_info").style.display = "block";
   }
}

function determineState(){
   var postcode = parseInt(document.getElementById("postcode").value);
   
   if(postcode >= 5000 && postcode <= 5999){
      //sa
      document.getElementById("state").selectedIndex = 1;
   }else if((postcode >= 1000 && postcode <= 2599) || (postcode >= 2619 && postcode <= 2898) || (postcode >= 2921 && postcode <= 2999)){
      //nsw
      document.getElementById("state").selectedIndex = 2;
   }else if((postcode >= 3000 && postcode <= 3999) || (postcode >= 8000 && postcode <= 8999)){
      //vic
      document.getElementById("state").selectedIndex = 3;
   }else if((postcode >= 4000 && postcode <= 4999) || (postcode >= 9000 && postcode <= 9999)){
      //qld
      document.getElementById("state").selectedIndex = 4;
   }else if((postcode >= 6000 && postcode <= 6797) || (postcode >= 6800 && postcode <= 6999)){
      //wa
      document.getElementById("state").selectedIndex = 5;
   }else if(postcode >= 800 && postcode <= 999){
      //nt
      document.getElementById("state").selectedIndex = 6;
   }else if(postcode >= 7000 && postcode <= 7999){
      //tas
      document.getElementById("state").selectedIndex = 7;
   }else if((postcode >= 200 && postcode <= 299) || (postcode >= 2600 && postcode <= 2618) || (postcode >= 2900 && postcode <= 2920)){
      //act
      document.getElementById("state").selectedIndex = 8;
   }
}


function tasks(g,o,s,fi){
document.getElementById("gender_select").selectedIndex = g;
document.getElementById("occupation").selectedIndex = o;
document.getElementById("state").selectedIndex = s;
generateField();
if(document.getElementById("further_info") != ""){
   document.getElementById("further_info").value = fi;
}
computeCost();
}