The second picture is the reference to the problem 1.40a on page 89 of the book. Thanks!

6. (0.5 point bonus) Problem 1.40a on page 89 of Sipser (3rd edition). Briefly: Let noprefix(a) = (w E Al no proper prefix of w is a member of A). Prove the regular languages are closed under the noprefix operation. 1.40 Recall that string x is a prefix of string y if a string z exists where xz -y, and that x is a proper prefix of y if in addition x y. In each of the following parts, we define an operation on a language A. Show that the class of regular languages is closed under that operation. Aa. NOPREFIX (A)-(w Al f A} no proper prefix of w 1s a member o