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

Example Input: Sentence: 'a young baseball player throws the ball as others watch'. Replace the letter 'a' with 'n' in the sentence.
Example Output: n young bnsebnll plnyer throws the bnll ns others wntch

Example Input: Sentence: 'an elephant in chains converses with a smaller elephant who is not wearing chains'. Replace the letter 'i' with 'm' in the sentence.
Example Output: an elephant mn chamns converses wmth a smaller elephant who ms not wearmng chamns

Example Input: Sentence: 'people standing next to a mirror with a reflection of a bus in it'. Replace the letter 'o' with 'y' in the sentence.
Example Output:
peyple standing next ty a mirryr with a reflectiyn yf a bus in it