Mar $3$ Bought laptops for $$7,200$ from Mouse Brand Computers. Terms were $1/10,$ n$/30.$

$8$ Sold a laptop for $$720$ on account. Cost was $$400.$ Terms were $1/15,$ n$/45.$

$11$ Paid for the computers purchased from Mouse Brand Computers.

$14$ Sold $5$ laptops. The regular price was $$4,000($all $5).$ Just Laptops gave a quantity discount of $5\%$ and the customer paid cash. The total cost was $$2,000.$

$20$ The customer who purchased the laptop on March $8$ paid in full.