A cell phone provider offers a plan that costs $20 per month plus $0.20 per text message sent or received. A comparable plan costs $30 per month but offers unlimited text messaging. Complete parts a. And b. Below.

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?