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

Example Input: Sentence: 'people are standing outside in the parking lot'. Replace the letter 'i' with 'z' in the sentence.
Example Output: people are standzng outszde zn the parkzng lot

Example Input: Sentence: 'a person is standing in the snow in skis'. Replace the letter 'g' with 'x' in the sentence.
Example Output: a person is standinx in the snow in skis

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