TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a mobile phone and a set of keys on a key chain'. Replace the letter 's' with 'j' in the sentence.

SOLUTION: a mobile phone and a jet of keyj on a key chain

PROBLEM: Sentence: 'a person flying a kite on the beach  between some trees'. Replace the letter 's' with 'k' in the sentence.

SOLUTION: a perkon flying a kite on the beach  between kome treek

PROBLEM: Sentence: 'a woman is standing next to a corner filled with street signs'. Replace the letter 'a' with 'b' in the sentence.

SOLUTION:
b wombn is stbnding next to b corner filled with street signs