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

Example Input: Sentence: 'a black cat is sniffing a glass bottle'. Replace the letter 'c' with 'f' in the sentence.
Example Output: a blafk fat is sniffing a glass bottle

Example Input: Sentence: 'nine geese flying south for the winter months'. Replace the letter 't' with 'f' in the sentence.
Example Output: nine geese flying soufh for fhe winfer monfhs

Example Input: Sentence: 'the two young elephants are standing beside a huge adult'. Replace the letter 'a' with 't' in the sentence.
Example Output:
the two young elephtnts tre sttnding beside t huge tdult