Thick ink is half immersed in the condensing pen tip. pen

Who can send Zhang Li Cai Hua?

Luoyang was once as expensive as money. -Paper

Solution: The first sentence is blackboard.

The second sentence is a pen: in calligraphy, to penetrate the back of the paper, we must first concentrate our luck.

The third sentence and the fourth sentence are paper: borrowing the allusion that Luoyang paper is expensive, Zhang Li's sentence of Cai Hua was written on "paper" and circulated, which made paper as expensive as paper money for a while.