In relation to discount terms, what does 5/7, n/30 mean?

		a. Invoice due on 5th July or 30th November.
		b. 50% discount if paid with 7 days, otherwise 30% discount.
		c. 50% discount, November 30th.
		d. 5% discount to be deducted from the invoice price if payment is made within 7 days or the full amount is due within 30 days of the invoice date.
		e. None of the above.