lootbox system with...

lootbox system with guaranteed common item, and a chance to win a bonus item belonging to one of 3 rarities (rare, very rare, ultra rare). there is a 10% chance to win a bonus Blueprint item on opening, and a guaranteed blueprint on 11th opening. Item is valued a certain fixed amount in "Fabric" currency depending on rarity group. i also want to keep track of how many ultra rare items are crafted by spending both Fabric (equal to item's worth in Fabric) and 1 Blueprint.