PQR Corporation purchased a patent for $50,000 on January 1, 2023, with a legal life of 20 years. Calculate the annual amortization expense using the straight-line method. Discuss the accounting treatment of intangible assets, such as patents, and the importance of amortization in allocating the cost of intangible assets over their useful lives. Additionally, explain how the amortization of intangible assets affects a company's income statement, balance sheet, and financial ratios.