At the faculty of Aerospace Engineering, 312 students study Random-processing methods, 234 students study Scramjet rocket engines and 112 students study them both. If every student in the faculty has to study one of the two subjects, how many students are there in the faculty of Aerospace Engineering? Choose one:
A) 430
B) 434
C) 438
D) 444
E) 446

Rationale: "312 + 234 - 112 ( since 112 is counted twice ) = 434 b is the answer"
Answer: B