Company Q sold merchandise to Company R on credit terms of 2/10, n/30. The invoice amount is $10,000. Company R returns $2,000 worth of merchandise. Calculate: a) The net amount Company R needs to pay if they avail the discount. b) The amount of discount if paid within the discount period. c) The net amount saved by availing the discount. d) The total sales revenue if the discount is not availed.