Product 'Fishy' is a highly perishable commodity which can be sold on the retail market for $\$ 20$ per case, or for animal food at $\$ 1$ per case. 'Fishy' costs $\$ 10$ per case from the wholesale market, and is only suitable for sale at the retail market for up to 24 hours after purchase. Orders for 'Fishy' must be placed in advance each day.

Vincent, a market stall owner, has kept the following records of sales of the 'Fishy' over the past 50 days, and correctly set up the following payoff table of his profits:

On the basis of using the maximin criteria, Vincent should supply _____________ cases of 'Fishy'.

Supply of cases Daily demand 10 cases 20 cases 30 cases 10 cases $100 $10 ($80) 20 cases $100 $200 $110 30 cases $100 $200 $300