[Insecure PRF] Assume that AES-128 (meaning AES with 128-bit key) is a secure PRF. Suppose that we need to implement a PRF with the key space and input space consisting of 128-bit strings, and the output space consisting of 129-bit strings. An engineer Alice proposes the following construction: use AES-128, so that the key space and input space are 128 bits, then take the 128-bit ciphertext block, XOR all the bits in the block and append the resulting bit at the end. Hereby, we get the 129-bit output space