Indicate the accounting concepts, principles, or constraints that underlie each of the following independent situations: accounting entity concept, going concern concept, cost-benefit constraint, expense recognition (matching principle), materiality constraint, revenue recognition principle, full disclosure principle, cost principle.

a. Dr. Lynn is a practicing pediatrician. Over the years, she has accumulated a personal investment portfolio of securities, virtually all of which have been purchased from her earnings as a pediatrician. The investment portfolio is not reflected in the accounting records of her medical practice.

b. A company purchases a desk tape dispenser for use by the office secretary. The tape dispenser cost \(\$ 25\) and has an estimated useful life of 15 years. The purchase is immediately expensed on the company's income statement.

c. A company sells a product that has a two-year warranty covering parts and labor. In the same period that revenues from product sales are recorded, an estimate of future warranty costs is recorded on the company's income statement.

d. A company is sued for \(\$ 1.5\) million by a customer claiming that a defective product caused an accident. The company believes that the lawsuit is without merit. Although the case will not be tried for a year, the company adds a note describing the lawsuit to its current financial statements.