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

Example Input: Sentence: 'a boy is sitting at a dinner table with his food'. Replace the letter 't' with 'r' in the sentence.
Example Output: a boy is sirring ar a dinner rable wirh his food

Example Input: Sentence: 'a giraffe walking in its natural habitat on the savannah'. Replace the letter 't' with 'u' in the sentence.
Example Output: a giraffe walking in ius nauural habiuau on uhe savannah

Example Input: Sentence: 'a toilet in a very small stall, with a plunger next to it'. Replace the letter 'a' with 'r' in the sentence.
Example Output:
r toilet in r very smrll strll, with r plunger next to it