Okay so...
.85/330 and 1.29/500
(Brand A) .0025757575757... and (Brand B) .00258
So it's Brand A (as shown above).
==========================================================
Same way to solve...
3.75/75 (Brand A) and 5.90/125 (Brand B)
.05 and .0472
So Brand B is the cheapest (Again with explanation above).