instruction:
In this task, you need to replace a letter in the sentence with another given letter.
question:
Sentence: 'a cat is watching a computer with a video of a cat'. Replace the letter 't' with 'a' in the sentence.
answer:
a caa is waaching a compuaer wiah a video of a caa

question:
Sentence: 'a blue and white train is coming down some tracks'. Replace the letter 'b' with 'u' in the sentence.
answer:
a ulue and white train is coming down some tracks

question:
Sentence: 'the big ben clock tower in the city of london england'. Replace the letter 't' with 'n' in the sentence.
answer:
nhe big ben clock nower in nhe ciny of london england