TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a tennis player throwing a ball at the ground'. Replace the letter 'r' with 'f' in the sentence.

SOLUTION: a tennis playef thfowing a ball at the gfound

PROBLEM: Sentence: 'people walk through a local fruit market in a city'. Replace the letter 'e' with 'n' in the sentence.

SOLUTION: pnopln walk through a local fruit marknt in a city

PROBLEM: Sentence: 'two cats are looking out of a window'. Replace the letter 't' with 'r' in the sentence.

SOLUTION:
rwo cars are looking our of a window