(4)For the purposes of sub-section (3)(b)(i),––(a)"pooling arrangement" means an agreement between two or more persons for providing services through a pool or operating one or more ships or inland vessels as the case may be, and sharing earnings or operating profits on the basis of mutually agreed terms;(b)"contract of affreightment" means a service contract under which a tonnage tax company agrees to transport a specified quantity of specified products at a specified rate, between designated loading and discharging ports over a specified period.