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

Example Input: Sentence: 'young boy leaping into air with tennis racket with dog below him'. Replace the letter 't' with 'r' in the sentence.
Example Output: young boy leaping inro air wirh rennis racker wirh dog below him

Example Input: Sentence: 'a hand held game or older cell phone'. Replace the letter 'o' with 'c' in the sentence.
Example Output: a hand held game cr clder cell phcne

Example Input: Sentence: 'a cluttered desk with open books and a crt monitor'. Replace the letter 'h' with 'x' in the sentence.
Example Output:
a cluttered desk witx open books and a crt monitor