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: 'a bike sitting parked next to a cart in front of some boxes'. Replace the letter 't' with 'x' in the sentence.
a bike sixxing parked nexx xo a carx in fronx of some boxes

Sentence: 'a big pretty white swan swimming in a river'. Replace the letter 'i' with 'y' in the sentence.

a byg pretty whyte swan swymmyng yn a ryver