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