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

Example Input: Sentence: 'a train moving on a track during the day'. Replace the letter 't' with 'q' in the sentence.
Example Output: a qrain moving on a qrack during qhe day

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 cow laying down in the grass next to a tree'. Replace the letter 'y' with 'j' in the sentence.
Example Output:
a cow lajing down in the grass next to a tree