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

Example Input: Sentence: 'the kitchen has a big screen tv and a lot of counter space'. Replace the letter 'h' with 'z' in the sentence.
Example Output: tze kitczen zas a big screen tv and a lot of counter space

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 white dog laying on top of the floor'. Replace the letter 'i' with 'f' in the sentence.
Example Output:
a whfte dog layfng on top of the floor