In this task, you need to replace a letter in the sentence with another given letter.

Example Input: Sentence: 'a group of young adults are engaged in outdoor exercise'. Replace the letter 'g' with 'n' in the sentence.
Example Output: a nroup of younn adults are ennaned in outdoor exercise

Example Input: Sentence: 'a group of sheep is standing in a grassy field'. Replace the letter 'g' with 'p' in the sentence.
Example Output: a proup of sheep is standinp in a prassy field

Example Input: Sentence: 'trucks are parked next to each other in a lot'. Replace the letter 'k' with 'p' in the sentence.
Example Output:
trucps are parped next to each other in a lot