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

Example Input: Sentence: 'a man is ordering food from a mobile food truck'. Replace the letter 'r' with 'q' in the sentence.
Example Output: a man is oqdeqing food fqom a mobile food tquck

Example Input: Sentence: 'a herd of zebra stand together and eat grass'. Replace the letter 'n' with 'r' in the sentence.
Example Output: a herd of zebra stard together ard eat grass

Example Input: Sentence: 'a child in a blue coat skiing on a ski slope'. Replace the letter 'u' with 't' in the sentence.
Example Output:
a child in a blte coat skiing on a ski slope