Tractor World Offers Warranties on All Their Tractors

Tractor World offers warranties on all their tractors.They estimate warranty expense at 2.4% of sales.At the beginning of 2013,the Estimated warranty payable account had a credit balance of $900.During the year,Tractor World had $285,000 of sales,and had to pay out $5,100 in warranty payments.
-At the end of the year,what balance in Estimated warranty payable would be included in the balance sheet?

A) $2,640
B) $5,100
C) $4,200
D) $6,840