Price discrimination is legal under which of the following conditions?
A) when a manufacturer and reseller have agreed upon a specified retail price for a product
B) when a manufacturer sells to retailers in different markets
C) when a seller can prove its costs are different when selling to different retailers
D) when a seller advertises prices that are not actually available to consumers
E) when a seller has not communicated with competitors before announcing prices
Answer: C) when a seller can prove its costs are different when selling to different retailers