def get_sum_of_discount_payments(cart_id)

			sum_of_discount_payments = 0
			
			get_discount_payments(cart_id).each do |dp|
				sum_of_discount_payments+= dp.amount
			end

			sum_of_discount_payments
		end
def get_sum_of_discount_payments(cart_id)

			sum_of_discount_payments = 0
			
			get_discount_payments(cart_id).each do |dp|
				sum_of_discount_payments+= dp.amount
			end

			sum_of_discount_payments
		end
will return the sum of the amounts of all successfull discount_payments.