Supermarket wars

Today Waitrose opened their supermarket in Exeter. This means that Exeter has the following supermarkets with carparks:
Tesco 3 (one large, two small)
Aldi 2
Lidl 2
Sainsbury 2
Morrisons 1
Waitrose 1
Cooperative 2

along with city centre stores which rely on city council or private car parks (Tesco, Sainsbury, Cooperative)

Now, if you are marketing one of these, the coming of a new one will have some effect on your sales. So what do you do? Encourage customers to stick with your business. The simplest way is to offer discounts. O.R. might be useful in suggesting how large the discounts should be. What have we received?

(1) £5 voucher for Waitrose if you spend £25 (in the local paper)
(2) £3 voucher at Sainsbury if you spend £15 (given when I spent £3 in the store; usually the offer is much less generous)
(3) four £5 vouchers at Tesco if we spend £20 (each voucher valid for a week)

So, the offers are all for a discount of 20 to 25%. I will not be surprised if we are given further vouchers in the next few weeks.

The next O.R. problem is to plan our shopping to take advantage of these offers! That looks like an allocation problem.