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

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 man that is holding a remote to a game'. Replace the letter 'a' with 'z' in the sentence.
Example Output: z mzn thzt is holding z remote to z gzme

Example Input: Sentence: 'three baseball players are standing while a crowd watches'. Replace the letter 'h' with 'o' in the sentence.
Example Output:
toree baseball players are standing woile a crowd watcoes