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

Ex Input:
Sentence: 'a dog laying in front of a horses stall with the horse peeking over the half door'. Replace the letter 'a' with 'b' in the sentence.

Ex Output:
b dog lbying in front of b horses stbll with the horse peeking over the hblf door

Ex Input:
Sentence: 'a close up of a train on train tracks at night'. Replace the letter 'n' with 'm' in the sentence.

Ex Output:
a close up of a traim om traim tracks at might

Ex Input:
Sentence: 'a horse drawn carriage riding down a rural country road'. Replace the letter 'n' with 'd' in the sentence.

Ex Output:
a horse drawd carriage rididg dowd a rural coudtry road