There are 3 math clubs in the school district, with 5, 7, and 8 students respectively. Each club has two co-presidents. If i randomly select a club, and then randomly select three members of that club to give a copy of $\emph{introduction to} \allowbreak\ \emph{counting and} \allowbreak\ \emph{probability}$, what is the probability that two of the people who receive books are co-presidents?.

Which of the following ideas did greek philosopher democritus contribute to the atomic theory? a. each object is made up of one atom, which varies in size from very small to very large. b. matter is composed of only one kind of particle, which can be easily destroyed. c. every element has a specific type of atom, which remains the same size in all forms of matter. d. all matter is composed of small particles, which combine to make larger objects.