Use the given information to find the number degrees of freedom, critical values X 2/L and X 2/R and the confidence interval estimate of lower case sigma. It is reasonable to assume that a simple random sample has been selected from a population with a normal distribution. Platelet count in women 98% confidence; n=21, s=65.5 mg. Please show the break down of how to solve this type of problem along with calculator routine, if has one.

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?