Gigi is going to buy 100 stickers.

Here is some information about the cost of stickers in two shops.

Stickers4u
Pack of 25 stickers for £2.25

World Stationery
Pack of 10 stickers for £1.75
Buy 1 pack get 1 pack free

Gigi wants to buy the stickers for the best possible price.

Which shop should Gigi buy the 100 stickers from?
You must show how you get your answer.