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

Example Input: Sentence: 'many people gathered on a sunny day flying kites'. Replace the letter 'e' with 'm' in the sentence.
Example Output: many pmoplm gathmrmd on a sunny day flying kitms

Example Input: Sentence: 'a group of three giraffes standing around a fence'. Replace the letter 't' with 'a' in the sentence.
Example Output: a group of ahree giraffes saanding around a fence

Example Input: Sentence: 'a couple of zebra standing next to a couple of giraffe'. Replace the letter 'a' with 'k' in the sentence.
Example Output:
k couple of zebrk stknding next to k couple of girkffe