1. Holly is making a cheese sauce.

She combines butter, flour, milk, and cheese so that

weight of butter : weight of flour : weight of milk : weight of cheese = 1 : 1 : 9 : 5 .

Holly needs to make 1.6 kg of cheese sauce all together.

Cheese costs £4.88 for 900 g.

Work out the cost of the cheese needed to make 1.6 kg of cheese sauce.