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

Example Input: Sentence: 'a red park ride bus at a curb with a green/white bus behind'. Replace the letter 'h' with 'x' in the sentence.
Example Output: a red park ride bus at a curb witx a green/wxite bus bexind

Example Input: Sentence: 'a person flying a kite on the beach  between some trees'. Replace the letter 's' with 'k' in the sentence.
Example Output: a perkon flying a kite on the beach  between kome treek

Example Input: Sentence: 'a man in a blue shirt looking at his cell phone'. Replace the letter 'm' with 'f' in the sentence.
Example Output:
a fan in a blue shirt looking at his cell phone