(2) Type of relationship required. Trade or business is related to exempt purposes, in the relevant sense, only where the conduct of the business activities has causal relationship to the achievement of exempt purposes (other than through the production of income); and it is substantially related, for purposes of section 513, only if the causal relationship is a substantial one. Thus, for the conduct of trade or business from which a particular amount of gross income is derived to be substantially related to purposes for which exemption is granted, the production or distribution of the goods or the performance of the services from which the gross income is derived must contribute importantly to the accomplishment of those purposes. Where the production or distribution of the goods or the performance of the services does not contribute importantly to the accomplishment of the exempt purposes of an organization,