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 small bird perched on a open window'. Replace the letter 'e' with 'r' in the sentence.
Example Output: a small bird prrchrd on a oprn window

Example Input: Sentence: 'three cows in a field near one another'. Replace the letter 'n' with 'o' in the sentence.
Example Output:
three cows io a field oear ooe aoother