(1) According to the meaning of the question, the retail volume is X, the wholesale volume is 3x, and the sales volume after warehousing is 200-4x, where 0≤x≤50.

Then y = (4500-1000) x+(3000-700) * 3x+(5500-1200) * (200-4x).

=3500x+6300x+860000-4300x

=860000-7400x, where 0≤x≤50.

(2) According to the meaning of the question, X should satisfy 200-4x≤80, and get 30≤x. Combined with the above, it can be seen that 30≤x≤50.

Then 222000≤7400x≤370000.

So 490000≤860000-7400x≤638000, that is, 490000≤y≤638000.

Therefore, the maximum profit should be 638,000 yuan.