This is a cryptology question from the book Introduction to Modern Cryptology by Katz and Lindell. A PDF of the book can be found online, if needed to reference for the question.

Here are passages from the book, showing the definitions referenced in the question.

3. Assume secure MACs exist. Prove that there exists a MAC that is secure (by Definition 4.2) but is not strongly secure (by Definition 4.3)