Answer:
a. Provide the journal entry for the estimated expense on September 30.
September 30, warranty liability
Dr Warranty expense 8,820
 Cr Warranty liability 8,820
b. Provide the journal entry for the October 15 warranty work. If an amount box does not require an entry, leave it blank.
October 15, warranty work
Dr Warranty liability 204
 Cr Inventory - parts 120
 Cr wages payable 84
Warranty expense must be recognized during the period that the associated sales are made, and as the expenses are accrued, you should debit the warranty liability account.