Deriving and changing the subject of formulae problem 28

At the market we bought 4 kg of prunes at 10 euros per kilogram, 3 kg of cottage cheese at 6 euros 99 cents per kilogram and 2 kg of cheese at 12 euros 75 cents per kilogram. At the cashier office we notice that we had a short fall of 10 euros 94 cents. Calculate how much the bill was and how much money we had in our wallet .