20. No dealer shall without reasonable excuse refuse to sell to any person any quantity of tea not exceeding the maximum fixed by or under this Ordinance. Explanation.- The possibility or expectation of obtaining a higher price at a later date shall not be deemed to be a reasonable excuse within the meaning of this section, but it shall not be a contravention of this section to refuse to supply tea to a retailer or a consumer in excess of his normal quota or reasonable requirements determined in accordance with the established system of distribution, in case such system is equitable and is in keeping with established commercial and trade practice.