Answer and Explanation:
The journal entries are given below:
1. Cash A/c Dr $19,000
Credit card expense A/c Dr  $1,000       ($20,000 × 5%)
    To Sales A/c               $20,000
(To record the received cash )
Cost of goods sold A/c Dr $15,000
    To Merchandise inventory A/c $15,000
(To record the inventory is sold at cost)
2. Accounts receivable A/c Dr $4,800
  Credit card expense A/c Dr  $200      ($5,000 × 4%)
    To Sales A/c               $5,000
(To record the merchandise is sold on credit)
Cost of goods sold A/c Dr $3,000
    To Merchandise inventory A/c $3,000
(To record the inventory is sold at cost)
Cash A/c Dr $4,800
   To Accounts receivable $4,800
(to record the cash is received)