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

Example Input: Sentence: 'a batter is batting at a baseball game'. Replace the letter 'b' with 'e' in the sentence.
Example Output: a eatter is eatting at a easeeall game

Example Input: Sentence: 'a train traveling through a dark tunnel next to green brush.'. Replace the letter 'r' with 'e' in the sentence.
Example Output: a teain teaveling theough a daek tunnel next to geeen beush.

Example Input: Sentence: 'a lady's hand is feeding a cat with a spoon'. Replace the letter 'a' with 's' in the sentence.
Example Output:
s lsdy's hsnd is feeding s cst with s spoon