Answer:
$80
Explanation:
Sarah and Best Groceries entered into an agreement or contract for purchasing necessary groceries on credit of a total value of 100 dollar. But Best Groceries made a breached and overcharged Sarah because the actual value of the items costs to 80 dollar. Best overcharged 20 dollar for the groceries. Thus when Sarah finds this and refuses to pay the amount, Best can collect only the actual value of the items which is 80 dollar.
Thus the answer is -- $80