(1)由题意得,销售量=250-10(x-25)=-10x+500,
则w=(x-20)(-10x+500)
=-10x2+700x-10000;
(2)w=-10x2+700x-10000=-10(x-35)2+2250.
∵-10<0,
∴函数图象开口向下,w有最大值,
当x=35时,wmax=2250,
故当单价为35元时,该文具每天的利润最大;
(3)A方案利润高.理由如下:
A方案中:20<x≤30,
故当x=30时,w有最大值,
此时wA=2000;
B方案中:,
故x的取值范围为:45≤x≤49,
∵函数w=-10(x-35)2+2250,对称轴为x=35,
∴当x=45时,w有最大值,
此时wB=1250,
∵wA>wB,
∴A方案利润更高.