Giovani operates his golf shop on a cash basis. On December 20, XX02 Giovani shipped and invoiced Pro Golf 50 cases of personalized golf balls for $6,000. Pro Golf contacted Giovani on December 23 and said the golf balls were not the quality expected and the personalized message was smudged on several of the golf balls. Pro Golf refused to remit full payment until they could negotiate a resolution. After inspecting the order on January 3, XX03, Giovani offered Pro Golf a 10% discount on future orders. How much of the sale is taxable to Giovani in XX02?