The average salary of the employees in a office is Rs.120/month.The avg salary of officers is Rs.420 and of non officers is Rs 110. If the no.of officers is 15,then find the No of nonofficers in the office.  Pick one: A) 400 B) 420 C) 430 D) 450 E) 510

Rationale: "let no . of non - officers be x 15 * 420 + x * 110 = ( x + 15 ) 120 x = 450 d"
Answer: D