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

Example Input: Sentence: 'one wall in the room is flanked by a lovely piece of furniture which displays several object d'art'. Replace the letter 'n' with 'z' in the sentence.
Example Output: oze wall iz the room is flazked by a lovely piece of furziture which displays several object d'art

Example Input: Sentence: 'a street pole stating three different street names and numbers'. Replace the letter 'm' with 't' in the sentence.
Example Output: a street pole stating three different street nates and nutbers

Example Input: Sentence: 'old, dented rail cars with gang graffiti line a railroad track'. Replace the letter 'a' with 'c' in the sentence.
Example Output:
old, dented rcil ccrs with gcng grcffiti line c rcilrocd trcck