② According to the meaning of the question: 400(x-5)-600≥800, the solution: x≥8.5,

∫5 < x≤ 10, and the price of each set meal is an integer.

The price per package cannot be lower than that of 9 yuan.

(2) When 5 < x ≤ 10, the sales volume is 400 copies, and x= 10,

Maximum daily net income y = 400×10-2600 =1400? (yuan)

When x > 10, y=(x-5)? [400-(x- 10)×40]-600 =-40(x- 12.5)2+ 1650，

Moreover, ∵x can only be an integer. ∴ When x= 12 or 13, the daily sales profit is the largest.

But in order to attract customers and increase sales, x= 12,

The daily profit at this time is:-40 (12-12.5) 2+1650 =1640 yuan;

A: When the price of each package is 12 yuan, the daily net income is 1640 yuan.