Exercise 3 (2 pts). The concatenation of strings a and y is the string ry. For example, the concatenation of the strings 1001 and 110 is the string 1001110. The concatenation operation for languages is defined as follows. Let A and B be languages. The concatenation of A and B is the language, denoted Ao B, consisting of all possible strings xy where z ? A and y ? B. Prove that if both A and B are in PSPACE, then A o B is also in PSPACE