BY or FOR?

Choose the option you think is correct

John did Paul's homework = John did Paul's homework __________ him.
BY
FOR
Paul's homework was done __________ John.
BY
FOR
__________ British standards, this weather is wonderful.
BY
FOR
You don't, __________ chance, know where I could buy a good dictionary, do you?
FOR
BY
__________ the way, there's a really good film on tonight, so I'm going to stay in and watch it.
BY
FOR
You need to MEMORISE this vocabulary = You need to learn this vocabulary __________ heart.
FOR
BY
We're not planning to make any major changes __________ the time being.
BY
FOR
10 ÷ 5 = 2 = Ten divided __________ five equals two.
BY
FOR
__________ rights, (por direito) I should give you a parking ticket.
BY
FOR
This house is heated __________ gas.
FOR
BY