The cost, in dollars, of shipping x computers to California for sale is 3000 + 100x. The amount received when selling these computers is 400x dollars. What is the least number of computers that must be shipped and sold so that the amount received is at least equal to the shipping cost?

To find the least number of computers that must be shipped and sold so that the amount received is at least equal to the shipping cost, we set up the inequality 400x >= 3000 + 100x. Simplifying this inequality gives 300x >= 3000, and dividing by 300 results in x >= 10. Therefore, at least 15 computers must be shipped and sold to cover the shipping cost, making choice B the correct answer. Choices A, C, and D are incorrect as they represent numbers less than 15, which would not cover the shipping cost.