Question: What is the first episode of the fifth season and the 81st overall episode of the American animated television sitcom "SpongeBob SquarePants" where Sirena Irwin voiced Mama Krabs?
Sentence (from "Friend or Foe (SpongeBob SquarePants)"): The episode originally aired on Nickelodeon in the United States on April 13, 2007.
Relevant evidence: No