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

Ex Input:
Sentence: 'a train traveling through a dark tunnel next to green brush.'. Replace the letter 'r' with 'e' in the sentence.

Ex Output:
a teain teaveling theough a daek tunnel next to geeen beush.

Ex Input:
Sentence: 'a ping pong player is in a ready stance to return the ball'. Replace the letter 'n' with 'e' in the sentence.

Ex Output:
a pieg poeg player is ie a ready staece to reture the ball

Ex Input:
Sentence: 'this is a kitten sitting on a laptop'. Replace the letter 'i' with 'w' in the sentence.

Ex Output:
thws ws a kwtten swttwng on a laptop