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

Example Input: Sentence: 'a cat sits on the floor next to a purse'. Replace the letter 'a' with 'b' in the sentence.
Example Output: b cbt sits on the floor next to b purse

Example Input: Sentence: 'a city street with cars and busses near buildings'. Replace the letter 'e' with 'd' in the sentence.
Example Output: a city strddt with cars and bussds ndar buildings

Example Input: Sentence: 'a man posing for the camera wearing a striped vest and hat with bow tie'. Replace the letter 'w' with 'k' in the sentence.
Example Output:
a man posing for the camera kearing a striped vest and hat kith bok tie