(a) A common purchaser purchasing in this state shall purchase ratably without unjust and unreasonable discrimination in favor of any owner or producer over any other owner or producer offering to sell oil produced from a field where it is a common purchaser or from fields in reasonably close proximity to each other where it is a common purchaser.
(b) If a purchaser is a common purchaser in more than one field in reasonably close proximity to each other, the commission may order the purchaser to purchase ratably from the fields involved in proportions that will prevent unjust and unreasonable discrimination among the fields.
(c) The commission may make inquiry in each field concerning the connections of the various producers and when unjust and unreasonable discrimination is found to be practiced by any common purchaser as defined in this chapter the commission shall issue an order to the common purchaser to make reasonable extensions of their lines and reasonable connections as will prevent the discrimination.