Mercury Inc. purchased equipment in 2019 at a cost of $400,000. The equipment was expected to produce 700,000 units over the next five years and have a residual value of $50,000. The equipment was sold for $210,000 part way through 2021. Actual production in each year was: 2019 = 100,000 units; 2020 = 160,000 units; 2021 = 80,000 units. Mercury uses units-of-production depreciation, and all depreciation has been recorded through the disposal date.

Required:
1. Calculate the gain or loss on the sale.
2. Prepare the journal entry to record the sale.
3. Assuming that the equipment was instead sold for $245,000, calculate the gain or loss on the sale.
4. Prepare the journal entry to record the sale in requirement 3.