So make sure that two building blocks are built at the same time.

Sticking to pies is the same principle.

Need classmate 1 classmate 2 classmate 3.

Same as 65438 +0 column+same as 2 column 4.

Then use 1 castle +3 train 4.

Then there is Tang 2 Castle+Tang 3 Castle 4.

So it is 4*3= 12 (minutes)

The rule is that you put a pie on your math book.

I forgot the formula. Sorry, give it to me personally ~ ~ ~

If you don't understand, you can ask.