Give a vector, if one exists, that generates the null space of the follow- ing systems of equations or matrices. Which of these seven sys- tems/matrices are invertible? [Consider the coefficient matrix and ig- nore the particular right-side values in parts (e) and (f).] T (b)2 51 2 1 -2 -2 4 -2 31

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?