Bags of flour come in 3 sizes:

Small bag: A 250 g bag costs 70p.
Medium bag: A 1 kg bag costs £2.90.
Large bag: A 3 kg bag costs £8.50.

Calculate the cost of 1 kg for the small and large bags.
Give your answer in pounds to 2 dp.
Write the bag that is the better value in the comments.