Direction: Answer Questions based on the following data and with the help of the given figure.

A = 30, represents total number of students in class studying Physics.

B = ?, represents total number of students studying Chemistry.

C = 40, represents total number of students studying Mathematics.

12 Students are studying Physics and Chemistry but not Mathematics.

16 Students are studying Chemistry and Mathematics but not Physics.

4 Students are studying Physics, Chemistry and Mathematics.