(2) Subsection (1) of this section does not prevent:
(a) Differentials which make only due allowance for differences in the cost of manufacture, sale or delivery, resulting from the differing methods or quantities in which the commodities are sold or delivered to purchasers.
(b) Persons engaged in selling goods, wares or merchandise, or service or output of a service trade, in commerce from selecting their own customers in bona fide transactions and not in restraint of trade.
(c) Price changes from time to time where in response to changing conditions affecting the market for or marketability of the goods concerned, such as but not limited to actual or imminent deterioration of perishable goods, obsolescence of seasonal goods, distress sales under court process, or sales in good faith in discontinuance of business in the goods concerned.