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 crowd watches as giraffes graze the tree tops at the zoo'. Replace the letter 't' with 'q' in the sentence.

SOLUTION: a crowd waqches as giraffes graze qhe qree qops aq qhe zoo

PROBLEM: Sentence: 'a converted vw bus holds a motorcycle in the back'. Replace the letter 'a' with 'n' in the sentence.

SOLUTION:
n converted vw bus holds n motorcycle in the bnck