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

Example Input: Sentence: 'little tubs of rice and mixed vegetables for a meal'. Replace the letter 't' with 'z' in the sentence.
Example Output: lizzle zubs of rice and mixed vegezables for a meal

Example Input: Sentence: 'a geoup of people on bicycles coming down a street'. Replace the letter 'i' with 'x' in the sentence.
Example Output: a geoup of people on bxcycles comxng down a street

Example Input: Sentence: 'a couple of guys standing up with some snowboards in hand'. Replace the letter 'a' with 'h' in the sentence.
Example Output:
h couple of guys sthnding up with some snowbohrds in hhnd