function calculate4(){
// ROCKFACE
	var rf12 = (document.gravelboards.amount.value * 6.50);
	var rf6 = (document.gravelboards.amount.value * 5.50);
	var rfd = (document.gravelboards.amount.value * 10);
// SMOOTH FACED
	var p12 = (document.gravelboards.amount.value * 6.75);
	var p6 = (document.gravelboards.amount.value * 5.75);
	var p7 = (document.gravelboards.amount.value * 10);
// WOODGRAIN SLEEPERS
	var woodg = (document.gravelboards.amount.value * 9);
// PICKET TOP
	var picket = (document.gravelboards.amount.value * 18.5);
// BALLUSTRADE
	var ball = (document.gravelboards.amount.value * 12.50);
// WOODEN
	var wood = (document.gravelboards.amount.value * 5.50);
//FORM FIELD VARIABLES
	var type = document.gravelboards.type.value;
//IF STATEMENTS
	if (type == "rf12"){
	document.gravelboards.total.value = rf12;
	}else if (type == "rf6"){
	document.gravelboards.total.value = rf6;
	}else if (type == "rfd"){
	document.gravelboards.total.value = rfd;
	}else if (type == "p12"){
	document.gravelboards.total.value = p12;
	}else if (type == "p6"){
	document.gravelboards.total.value = p6;
	}else if (type == "p7"){
	document.gravelboards.total.value = p7;
	}else if (type == "woodg"){
	document.gravelboards.total.value = woodg;
	}else if (type == "picket"){
	document.gravelboards.total.value = picket;
	}else if (type == "ball"){
	document.gravelboards.total.value = ball;
	}else if (type == "wood"){
	document.gravelboards.total.value = wood;
	}
}