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

Example Input: Sentence: 'a crooked street sign on a damaged sidewalk'. Replace the letter 'm' with 'u' in the sentence.
Example Output: a crooked street sign on a dauaged sidewalk

Example Input: Sentence: 'some tracks for a rail way system near a building'. Replace the letter 'a' with 'h' in the sentence.
Example Output: some trhcks for h rhil why system nehr h building

Example Input: Sentence: 'a train traveling on a train track near a field with cows in it'. Replace the letter 'n' with 'y' in the sentence.
Example Output:
a traiy traveliyg oy a traiy track year a field with cows iy it