Find the cost of making 125 cylindrical tennis ball containers that have a diameter of 7cm and a height if 21cm, and the metal costs $4.50 per square metre ( metal base but open at the top)
hint- the answer is $28.14. i just need the working out ty

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?