A publisher has orders for 500 copies of a certain textbook from San Francisco and 600 copies from Sacramento. The publisher has 700 copies in a warehouse in Novato and 400 copies in a warehouse in Lodi. It costs $5 to ship a textbook from Novato to San Francisco, but it costs $10 to ship it to Sacramento. It costs $15 to ship a textbook from Lodi to San Francisco, but it costs $4 to ship it from Lodi to Sacramento. The goal of the publisher is to minimize its total shipping cost.

Please formulate this problem with objective function and constraints.