function FpAmount(b,f,d,t) {
			
		var WrkTable=document.getElementById("FPamountText");
		var WrkTable2=document.getElementById("FPamountLava");
		WrkTable.style.visibility="visible";
		WrkTable2.style.visibility="visible";	
		
		var amount = 0;
		var a =0;
		var base =0;
		var lava = 0;

		
	   amount = getAmount(b,f,d,t);
	   lava = getlava(t,amount);

      
		WrkTable.value = "You will need " + amount + " lbs. of Glass for a " + t + " inch fill.";
		WrkTable2.value = lava + " lbs. of Pea Size Lava Rock will give you 1 inch of lava fill.";
	
	}

	
	function getAmount(b,f,d,t) {
		
		var amount=0;
		var base =0;
		var abase =0;
		
        bn = b - 0;
        fn = f - 0;
		dn = d - 0;
		tn = t - 0;

        abase = (bn + fn)/2 ; 
		base = (abase * dn * tn) / 231;
		amount = (Math.round(base * 12));

		return amount;
	}

	function getlava(t,amount) {
		

		var lava = 0;

		amountn = amount - 0;
		tn = t - 0;

		lava = Math.round(((1/tn) * amountn) * .7);

		return lava;
	}