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

Example Input: Sentence: 'a fire fighter climbs onto the roof of a market with a ladder'. Replace the letter 'r' with 'k' in the sentence.
Example Output: a fike fightek climbs onto the koof of a makket with a laddek

Example Input: Sentence: 'lose up of various trays of croissants and muffins'. Replace the letter 'n' with 'f' in the sentence.
Example Output: lose up of various trays of croissafts afd muffifs

Example Input: Sentence: 'a picture of a person holding some food'. Replace the letter 'o' with 'z' in the sentence.
Example Output:
a picture zf a perszn hzlding szme fzzd