Answer: enforceable due to leading object rule.
Step-by-step explanation:
Enforceable is defined as any action that can be implemented or can be made effective.
Leading object rule is the regulation that is defined for contract law in which written document is not required because promisor promises to pay the debt of another party for the main purpose of their own benefit.
According to the situation described in question, Tuan's guarantee for paying the debt can happen under the leading object rule where he would be paying as the shareholder of Entertainment Inc. He will also receive the benefit earned by the incorporation thus, he can orally agree to the promise.