TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a herd of black cattle grazing and lounging in a green field'. Replace the letter 'a' with 'q' in the sentence.

SOLUTION: q herd of blqck cqttle grqzing qnd lounging in q green field

PROBLEM: Sentence: 'a group of young adults are engaged in outdoor exercise'. Replace the letter 'g' with 'n' in the sentence.

SOLUTION: a nroup of younn adults are ennaned in outdoor exercise

PROBLEM: Sentence: 'a yellow and red train traveling down train tracks'. Replace the letter 'i' with 'o' in the sentence.

SOLUTION:
a yellow and red traon travelong down traon tracks