The rate of elimination of a certain drug from a bloodstream is k times the mass, x mg, of the drug still present at the time t . The drug is intravenously fed into the bloodstream at an infusion rate of r mg per minute such that dx/dt=-kx + r . Assuming that x = 0 when t = 0, (a) show that x=(r/k)(1-e^-kt
b) estimate the infusion rate that results in a long-term amount of 50mg of drug

in the bloodstream, given that
k=In2/100

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?