Final answer:
Dyckman Dealers should carry the trading security investment in Thomas Corporation at its fair market value of $20,000, as dictated by accounting standards.
Step-by-step explanation:
The investment in Thomas Corporation by Dyckman Dealers, which is accounted for as a trading security, should be recorded on the balance sheet at its fair market value.
In this case, the fair market value is given by the current trading price on the New York Stock Exchange, which is $20,000.
Management's belief that the market is overvalued and their internal valuation of $18,000 is irrelevant for accounting purposes since Generally Accepted Accounting Principles (GAAP) dictate that trading securities must be carried at fair value on the balance sheet.