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

Example Input: Sentence: 'a small bird perched on a open window'. Replace the letter 'e' with 'r' in the sentence.
Example Output: a small bird prrchrd on a oprn window

Example Input: Sentence: 'two tennis players shaking hands across the net'. Replace the letter 't' with 's' in the sentence.
Example Output: swo sennis players shaking hands across she nes

Example Input: Sentence: 'skateboarder jumping over a rail in a basketball court'. Replace the letter 'a' with 'y' in the sentence.
Example Output:
skyteboyrder jumping over y ryil in y bysketbyll court