Solution: Suppose the first batch buys X disks, and the second batch buys 2X disks.

The average cost is [16X/3+ 12*2X/4].

Then [16x/3+12 * 2x/4] * (1+20%) = k * (x+2x)/3.

Divide both sides by x at the same time to get K= 13.6.

the second question

There is no simple way, push it bit by bit and pay attention to the requirements in the topic. At every intersection, people will only go east and north.

The ratio of people at point B to point C is 5:4.

So the answer is 32.