## Discussion Forum

Que. | Consider two languages L1 and L2 each on the alphabet ∑. Let f : ∑ → ∑ be a polynomial time computable bijection such that (∀ x) [x ∈ L1 iff f(x) ∈ L2]. Further, let f^-1 be also polynomial time computable. Which of the following CANNOT be true? |

a. | L1 ∈ P and L2 is finite |

b. | L1 ∈ NP and L2 ∈ P |

c. | L1 is undecidable and L2 is decidable |

d. | L1 is recursively enumerable and L2 is recursive |

Answer:L1 is undecidable and L2 is decidable |