Soon after December $31,$ Year $7,$ the auditor requested a depreciation schedule for trucks of Jarrett Trucking Company, showing the additions, retirements, depreciation, and other data affecting the income of the company in the $4-$year period Year $4$ to Year $7,$ inclusive. The following data were in the Trucks account as of January $1,$ Year $4$:

Truck no$.1$ Purchased January $1,$ Year $1$ $$12,000$

Truck no$.2$ Purchased July $1,$ Year $110,400$

Truck no$.3$ Purchased January $1,$ Year $312,800$

Truck no$.4$ Purchased July $1,$ Year $315,000$

Balance January $1,$ Year $4$ $$50,200$

The Accumulated Depreciation$$Trucks account, previously adjusted to January $1,$ Year $4,$ and duly entered in the ledger, had a balance on that date of $$16,460.$ This amount represented the straight$-$line depreciation on the four trucks from the respective dates of purchase, based on a $5-$year life and no residual value. No debits had been made to this account prior to January $1,$ Year $4.$

Transactions between January $1,$ Year $5,$ and December $31,$ Year $7,$ and their record in the ledger were as follows:

$1.$ July $1,$ Year $4$: Truck no$.1$ was sold for $$1,000$ cash. The entry was a debit to Cash and a credit to Trucks, $$1,000.$

$2.$ January $1,$ Year $5$: Truck no$.3$ was traded for a larger one $($no$.5)$ with a $5-$year life. The agreed purchase price was $$12,000.$ Jarrett paid the other company $$1,780$ cash on the transaction. The entry was a debit to Trucks, $$1,780,$ and a credit to Cash, $$1,780.$

$3.$ July $1,$ Year $6$: Truck no$.4$ was damaged in a wreck to such an extent that it was sold as junk for $$50$ cash. Jarrett received $$950$ from the insurance company. The entry made by the bookkeeper was a debit to Cash, $$1,000,$ and credits to Miscellaneous Revenue, $$50,$ and Trucks, $$950.$

$4.$ July $1,$ Year $6$: A new truck $($no$.6)$ was acquired for $$20,000$ cash and debited at that amount to the Trucks account. The truck has a $5-$year life.

Entries for depreciation had been made at the close of each year as follows: Year $4,$ $$8,840$; Year $5,$ $$5,436$; Year $6,$ $$4,896$; Year $7,$ $$4,356.$

Required:

$1.$ Next Level For each of the $4$ years, calculate separately the increase or decrease in earnings arising from the company$$s errors in determining or entering depreciation or in recording transactions affecting trucks.

$2.$ Prove your work by one compound journal entry as of December $31,$ Year $7$; the adjustment of the Trucks account is to reflect the correct balances, assuming that the books have not been closed for Year $7.$