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

Sentence: 'a tower type building structure with a large clock and many windows in front of a cloudy blue sky'. Replace the letter 'n' with 'x' in the sentence.
a tower type buildixg structure with a large clock axd maxy wixdows ix froxt of a cloudy blue sky

Sentence: 'traffic congestion with cars and an electric tram'. Replace the letter 'a' with 'k' in the sentence.
trkffic congestion with ckrs knd kn electric trkm

Sentence: 'two flavored donuts, for sale behind the case'. Replace the letter 'f' with 't' in the sentence.
two tlavored donuts, tor sale behind the case