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

Example Input: Sentence: 'a zebra standing by a pile of large rocks'. Replace the letter 'i' with 'x' in the sentence.
Example Output: a zebra standxng by a pxle of large rocks

Example Input: Sentence: 'a gate with a stop sign blocking the road'. Replace the letter 'h' with 'y' in the sentence.
Example Output: a gate wity a stop sign blocking tye road

Example Input: Sentence: 'an antique clock sits up against a wall'. Replace the letter 'c' with 'g' in the sentence.
Example Output:
an antique glogk sits up against a wall