Susan says that the ratio of cups of water to total cups of ingredients is 1: 2 because these is twice as much water as there is rice. is this the correct ratio? explain why or why not, and if not, give the correct ratio.

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?