To determine the money she could have saved if she paid the furniture in full, you have to determine the total amount she will pay when she completes the 18 payments and subtract the price of the furniture from that:
Total amount= 267.98*18
Total amount=4,823.64
$4,823.64-$4,200= $623.64
She have saved $623.64 if she paid for the furniture in full.
