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

Example Input: Sentence: 'people walk through a local fruit market in a city'. Replace the letter 'e' with 'n' in the sentence.
Example Output: pnopln walk through a local fruit marknt in a city

Example Input: Sentence: 'a close up of a grassy beach showing an umbrella and wind board'. Replace the letter 'a' with 'f' in the sentence.
Example Output: f close up of f grfssy befch showing fn umbrellf fnd wind bofrd

Example Input: Sentence: 'a white boom box with an mp3 player on top of it'. Replace the letter 'i' with 'p' in the sentence.
Example Output:
a whpte boom box wpth an mp3 player on top of pt