Can you solve it? Would you get into Oxford?

Try your luck at its fiendish maths entrance exam

UPDATE: To read the solution click here

Last week about 3,500 of Britain's most mathematically gifted sixth formers sat Oxford university's annual Mathematics Admissions Test.

The exam is designed to test "mathematical understanding"rather than a breadth of knowledge." Today's puzzle is taken from a recent paper. It's about stacking items in a shopping bag.