In a survey of 150 students, preferences for three academic subjects—Mathematics (M), Physics (P), and Chemistry (C)—were recorded. It was found that $n(M) = 70$, $n(P) = 60$, and $n(C) = 50$. The number of students who like at least one subject is $120$. The number of students who like exactly one subject is $75$. How many students like exactly two subjects?