A change is an event that some cells content is overwritten by a different symbol. Notice that, if initially a cell is empty, a change occurs when it holds a non-null symbol. Non-deterministic Turing machine M is 10- change if during any computation of M on any input word, there are at most 10 changes. (1). What is the smallest class of languages that 10-change Turing machines can accept? Prove your answer. (2). (hard) A Turing machine M is 10-change-per-cell if during any computation of M on any input word, there are at most 10 changes occurring at each cell. Prove that any deterministic Turing machine can be simulated by a 10-change-per-cell one.