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 plate with some mean and vegetables on it'. Replace the letter 'a' with 'f' in the sentence.

SOLUTION: f plfte with some mefn fnd vegetfbles on it

PROBLEM: Sentence: 'a boy with two bicycles reading a newspaper'. Replace the letter 'b' with 't' in the sentence.

SOLUTION:
a toy with two ticycles reading a newspaper