Answer:
a. Patent development and registration costs incurred in 2020.
Dr Patent 11,200 (only patent registration fees)
Dr Research and development expense 49,600
Cr Accumulated depreciation 6,400
Cr Cash 54,400
b. Legal fees paid in 2021.
Dr Patent 4,800
Cr Cash 4,800
c. Amortization expense in 2021.
Dr Amortization expense 607.50
Cr Patent 607.50
($11,200/20 x 9/12) + ($15,000/20 x 3/12) = $607.50
d. Amortization expense in 2022
Dr Amortization expense 750
Cr Patent 750