10. Can a set and its complement BOTH be non-r.e. ? Justify your answer. 11. Is the set L = { i such that M_i accepts only one string} an r.e. set ? 12. Formally show that the set K has an undecidable membership problem. 13. How would one go about proving that a given set is not computable (r.e.) ? 10. Can a set and its complement BOTH be non-r.e. ? Justify your answer. 11. Is the set L = { i such that M_i accepts only one string} an r.e. set ? 12. Formally show that the set K has an undecidable membership problem. 13. How would one go about proving that a given set is not computable (r.e.)