(1) y = 50x + 45*(80-x) = 5x + 3600, 0.6(80-x) + 1.1x <=700.9(80-x) + 0.4x <= 5240<= x <= 442. y = 5x + 3600, x=44 时, 利润最大, 为5*44 + 3600 = 3820 元