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

Example Input: Sentence: 'a bunch of signs on a pole on the street'. Replace the letter 'c' with 's' in the sentence.
Example Output: a bunsh of signs on a pole on the street

Example Input: Sentence: 'a painting of scissors going to cut a chain with a lock'. Replace the letter 'g' with 'v' in the sentence.
Example Output: a paintinv of scissors voinv to cut a chain with a lock

Example Input: Sentence: 'a man is holding a rope and surf on the water'. Replace the letter 'f' with 'u' in the sentence.
Example Output:
a man is holding a rope and suru on the water