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

Example Input: Sentence: 'many street signs in front of a building while it is snowing'. Replace the letter 'r' with 'x' in the sentence.
Example Output: many stxeet signs in fxont of a building while it is snowing

Example Input: Sentence: 'the bus is trying to navigate though the london traffic'. Replace the letter 'a' with 'l' in the sentence.
Example Output: the bus is trying to nlviglte though the london trlffic

Example Input: Sentence: 'a painted fire hydrant in the middle of grass'. Replace the letter 'h' with 'p' in the sentence.
Example Output:
a painted fire pydrant in tpe middle of grass