instruction:
In this task, you need to replace a letter in the sentence with another given letter.
question:
Sentence: 'two men and a dog are standing beside a building'. Replace the letter 'b' with 'y' in the sentence.
answer:
two men and a dog are standing yeside a yuilding

question:
Sentence: 'a u.s. military helicopter landing or taking off'. Replace the letter 'i' with 'l' in the sentence.
answer:
a u.s. mllltary hellcopter landlng or taklng off

question:
Sentence: 'a ferry boat travels on a river, with buildings and a large clock in the background'. Replace the letter 'r' with 'n' in the sentence.
answer:
a fenny boat tnavels on a niven, with buildings and a lange clock in the backgnound