First, find the total mass in Kg.
We have four bags and they each weigh 2.5 Kg. Multiply the amount of bags by the weight of each bag. 4 bags x 2.5 Kg = 10 Kg of Cat food
Now, to convert from Kgs to Lbs, multiply the total weight by 2.205 (since one Kg is about 2.205 lbs)
10 Kg x 2.205 = 22.05 Lbs
That's a good amount of food for any cat