function calulate_payment(form){
	
	var nCost
	nCost = ((form.base_cost.value * form.num_eyes.options[form.num_eyes.selectedIndex].value) / 12)
	//alert (nCost)
	nCost = Math.floor(nCost*100)/100
	
	form.monthly_payment.value = "$" + nCost
	
	return false
	
}