y =( 160-2x)x-(500+30x)=-2 x2+ 130 x-500，
From y= 1500,-2x2+130x-500 =1500,
∴x2-65x+ 1000=0，
∴(x-40)(x-25)=0，
X 1=40，x2 = 25
When the daily output is four or five pieces, the monthly profit 1500 yuan.
(2) According to (1), y =-2x2+130x-500 =-2 (x-652) 2+1612.5,
∵x is a positive integer. When ∴x=32 or 33, the maximum value of y is 16 12 yuan.
∴ When the daily output is 32 or 33 pieces, the maximum profit can be 16 12 yuan.