Summer Empowerment

Me and my sister in a souvenir shop :

Sister: Oooh this is so cute!
(My sister points at a crystal cube with customized 3D portrait inside)
Me: yeah it is alright
(Not really interested)
Sister: We should totally get our pics done
Me: yeah ok
(Still not interested)
Sister: which size should we take?
Me: hmmm
(I had to look up and see what she was talking about.
I see 3 piles of stacked crystal cubes:
The pile on left had 3 crystals of 3 different sizes
The pile in the middle had 3 crystals of 2 sizes,
The pile on the right; I can't really remember.)

Me: Excuse me, which one of those is the medium size?
(Silly Sales Attendant -SSA- points at the pile on the left)
SSA: if this one is small and this one is large, which size do you think is the one in the middle?
(Group of SSA starts laughing)
Me: Ok so what about the ones in here?
( I point at the pile in the middle)
SSA: those two are small but this one is large.
(SSAs laugh some more)
Me: see that is why I asked
SSA: It is up to me!
Me: you know because of that attitude of yours am not going to buy anything. Your Bad!

Me and Sis walk out of shop!