What is the expected value of a stock investment of $20,000 that has a 25% chance of decreasing to a value of $18,000, a 25% chance of maintaining a value of $20,000, and a 50% chance of increasing to a value of $25,500?

Aclassroom is made up of 11 boys and 14 girls. the teacher has four main classroom responsibilities that she wants to hand out to four different students (one for each of the four students). if the teacher chooses 4 of the students at random, then what is the probability that the four students chosen to complete the responsibilities will be all boys?