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

Example Input: Sentence: 'a herd of cattle standing on a lush green field'. Replace the letter 'g' with 'f' in the sentence.
Example Output: a herd of cattle standinf on a lush freen field

Example Input: Sentence: 'a man eats food that is inside a banana peel'. Replace the letter 'n' with 'k' in the sentence.
Example Output: a mak eats food that is ikside a bakaka peel

Example Input: Sentence: 'a lady swinging tennis racket at a ball above her head'. Replace the letter 'a' with 'j' in the sentence.
Example Output:
j ljdy swinging tennis rjcket jt j bjll jbove her hejd