On a particularly artistic fruit stall, a pile of oranges is arranged to form a truncated square pyramid. Each layer is a square, with the lengths of the side of successive layers reducing by one orange (as shown below). The bottom layer measures 2n Xx 2n oranges, and there are n layers. Prove that the number of oranges used is n(2n + 1)(7n+ 1). (i) (ii) How many complete layers can the person setting up the stall use for this arrangement, given their stock of 1000 oranges? How many oranges are left over?