When x > 15,

Daily sales: 400-40 (x-15) =1000-40x, and the profit per share is (x-8) yuan.

y =( 1000-40x)(x-8)-800 =-40x 2+ 1320 x-8800；

(2) From the meaning of the question: 400x-4000≥ 1200,

Solution: x ≥ 13.

Therefore, the price of each package should be 13 yuan.

(3) When x≤ 15, the maximum value of y =2000.

When x > 15, y =-40x2+1320x-8800 =-40 (x-16.5) 2+2090.

∵ The price of X (yuan) is an integer, which not only attracts customers, but also makes the daily sales volume bigger and the daily net income higher.

When x= 16, the maximum value of y =2080,

To sum up, the price of each package should be 16 yuan, and the daily net income is 2080 yuan.