Will has 7/8 gallon of cold water in the refrigerator. During the day, he drinks 3/4 gallon of the water. How much cold water does he have left at the end of the day?

A.1/8 gallon
B.1/4 gallon
C.1/2 gallon
D.1 gallon

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?