From a group of 8 people, including george and nina, 3 people are to be selected at random to work on a certain project. what is the probability that the 3 people selected will include george but not nina?

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?