Prepare the following journal entries and calculations:

a) A patent that was purchased for $100,000 earlier this year expires in 15 years and is expected to have value for 4 years. Submit the adjustment entry to amortize the patent for the current year.

b) Mining rights over a mineral deposit estimated at 4,000,000 tons of mineral were acquired for $4,000,000. Submit the adjustment entry to record the depletion of the current year, during which 350,000 tons of ore were extracted.

c) The legal expenses incurred to defend the rights granted by the patent were $42,000. The patent only has a legal life of 5 years. Determine the amount to be amortized for the current year.