A yuan for the first time and B yuan for the second time.
A * * * buy 2 kg.
Spend money ax+bx
Average value (ax+bx)/2x=(a+b)/2.
Small flowers spend y yuan each time.
Then buy y/a+y/b=y(a+b)/ab kg.
Average 2y/[y(a+b)/ab]=2ab/(a+b)
(a+b)/2-2ab/(a+b)
=[(a+b)^2-4ab]]/2(a+b)
=(a-b)^2/2(a+b)>; 0
So Xiao minggui
Xiaohua is very cheap