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

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

Example Input: Sentence: 'a woman is on skis riding down the snow covered sloped'. Replace the letter 'd' with 'q' in the sentence.
Example Output: a woman is on skis riqing qown the snow covereq slopeq

Example Input: Sentence: 'a picture of a bunch of zebras backends'. Replace the letter 'b' with 'l' in the sentence.
Example Output:
a picture of a lunch of zelras lackends