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

Ex Input:
Sentence: 'a blue and white train is coming down some tracks'. Replace the letter 'b' with 'u' in the sentence.

Ex Output:
a ulue and white train is coming down some tracks

Ex Input:
Sentence: 'a man stands next to a basketball as it sits on the floor'. Replace the letter 'n' with 'o' in the sentence.

Ex Output:
a mao staods oext to a basketball as it sits oo the floor

Ex Input:
Sentence: 'three people are posing for a picture on the beach'. Replace the letter 'h' with 'i' in the sentence.

Ex Output:
tiree people are posing for a picture on tie beaci