TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a yellow fire truck parked in a parking lot'. Replace the letter 'a' with 'y' in the sentence.

SOLUTION: y yellow fire truck pyrked in y pyrking lot

PROBLEM: Sentence: 'a person under an open umbrella in the sand'. Replace the letter 'd' with 'h' in the sentence.

SOLUTION: a person unher an open umbrella in the sanh

PROBLEM: Sentence: 'some zebras and a brown animal some grass and bushes'. Replace the letter 'a' with 'l' in the sentence.

SOLUTION:
some zebrls lnd l brown lnimll some grlss lnd bushes