31. A middle school has decided to organize a study tour for some classes. There are 16 teachers and 284 students. There are two types of large buses available: Bus A can carry 30 people and costs 300 yuan to rent; Bus B can carry 42 people and costs 400 yuan to rent. The school plans for the total rental cost of the study tour to not exceed 3100 yuan. For safety, each bus must have at least 2 teachers. There are $\qquad$ different rental plans, and the minimum rental cost is $\qquad$ yuan.
Answer: 3,2900