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

Example Input: Sentence: 'a plate with some mean and vegetables on it'. Replace the letter 'a' with 'f' in the sentence.
Example Output: f plfte with some mefn fnd vegetfbles on it

Example Input: Sentence: 'a girl riding a horse is jumping the log'. Replace the letter 'a' with 't' in the sentence.
Example Output: t girl riding t horse is jumping the log

Example Input: Sentence: 'a man eating a donut by a big window'. Replace the letter 'g' with 'u' in the sentence.
Example Output:
a man eatinu a donut by a biu window