function calculate(form) {
								w = form.weight.value - 0;
								p = form.price.value - 0;
								s = form.service.value;
								threshold = form.threshold.value;
								if (w >= threshold)	{ s = 7.5 };
								t = w * p;
								amendedtotal = t - (t * s / 100)
								form.total.value = amendedtotal.toFixed(2);
								}