The average height of 20 students in a class was calculated as 175 cm. It has later found that the height of one of the students in the class was incorrectly written as 151 cm whereas the actual height was 111 cm. What was the actual average height of the students in the class?  Choose the correct choice:
A) 174 cm  B) 173 cm  C) 172 cm  D) 171 cm  E) 170 cm

Rationale: "the total height was 40 cm too much . the average height should be reduced by 40 cm / 20 = 2 cm the answer is b ."
Answer: B