According to the number line, what is the distance between points A and B? A
B
_16-14-12-10 -3 -6 1 -2 0 2 4 6 8 10 12 14 16
6 units
7 units
12 units
14 units

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?