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At least two people have the same birthday in a school of 150 students

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

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?