In a school, there are 150 students. Out of these 80 students enrolled for mathematics class, 50 enrolled for English class, 60 enrolled for physics class. The student enrolled for English cannot
attend any other class , but student of mathematics and physics can take two courses at a
time. Find the number of students who have taken both physics and mathematics.
a. 40
b. 30
c. 50
d. 20