You are a consumer. Now choose your utility function:
U = 10 20 30 40 50 A + 100 200 300 B - 0.25 0.5 0.75 1 A2 - 0.25 0.5 0.75 1 B2
The price of a jar of peanut butter is £ 4 6 8 10 :00
The price of a loaf of bread is £ 3 5 7 9 :00
And you have a maximum budget of £ 1000 2000 3000 4000 5000 :00