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

Ex Input:
Sentence: 'a photo of a river with a train bridge across it'. Replace the letter 'r' with 'f' in the sentence.

Ex Output:
a photo of a fivef with a tfain bfidge acfoss it

Ex Input:
Sentence: 'a large white sign with black lettering leaning against a metal fence'. Replace the letter 'e' with 'j' in the sentence.

Ex Output:
a largj whitj sign with black ljttjring ljaning against a mjtal fjncj

Ex Input:
Sentence: 'a street sign with a sky in the background'. Replace the letter 'e' with 'n' in the sentence.

Ex Output:
a strnnt sign with a sky in thn background