
Answer:
August 1, sold goods on account terms 3/10, n/30
Dr Account receivable 5,000
  Cr Sales revenue 5,000
Dr Cost of goods sold 3,000
  Cr Merchandise inventory 3,000
Dr Accounts receivable (freight) 320
  Cr Cash 320
When FOB shipping point is used, buyer pays the freight. When FOB destination is used, the  seller pays the freight.
August 7, damaged merchandise returned
Dr Sales returns and allowances 1,200
  Cr Accounts receivable 1,200
Dr Merchandise inventory 720 (approximately 60% since $3,000/$5,000)
  Cr Cost of goods sold 720
August 11, invoice and freight charges collected
Dr Cash 4,006
Dr Sales discounts 114 (3% of $3,800)
  Cr Accounts receivable 4,120 ($3,800 for the merchandise and $320 for the prepaid freight)