You have been hired as the new controller for the Ralston Company. Shortly after joining the company in 2024, you discover the following errors related to the 2022 and 2023 financial statements:
a. Inventory at 12/31/2022 was understated by $6,000.
b. Inventory at 12/31/2023 was overstated by $9,000.
c. On 12/31/2023, inventory was purchased for $3,000. The company did not record the purchase until the inventory was paid for early in 2024. At that time, the purchase was recorded by a debit to purchases and a credit to cash. The company uses a periodic inventory system.

Required:
1. Assuming that the errors were discovered after the 2023 financial statements were issued, analyze the effect of the errors on 2023 and 2022 cost of goods sold, net income, and retained earnings. (Ignore income taxes.)
2. Prepare a journal entry to correct the errors.
3. Will Ralston account for the change (a) retrospectively or (b) prospectively?