I have been to Dingzhou.

The calculation of definite integrals is an important part of calculus.

The fixed price of this product is 3000 yen.

Mr. Sadayoka is my best friend.

Teisuke is my best friend.

Mr. Teisuke is my best friend.

I was asked to revise this thesis.

He stayed up all night to revise the thesis.

I live in Baoding city.

His success is based on the assumption that he is a hard worker.