please explain the 5th and 6th question

3) January 1: Purchased 50 personal computers at a cost of $1,500 each. The computers were purchased from supplier A and were paid for in cash. 4) January 4: Purchased from Supplier B, on account, 50 printers at a cost of $450 each. The terms of the purchase were 2/10,n/30. 5) January 5: Sold 40 personal computers for $2,550 each to a local university. The terms of the sale were 2/10,n/30. 6) January 14: Sold on account 39 printers for $750 each to a copy/printing store. 7) January 14: The local university paid its outstanding balance in full. 8) January 14: Paid Supplier B the full balance due. 9) January 16: Issued 1,000 shares for $50 a share. Carly and Carl purchased the shares in equal quantities and they paid for the shares in cash