How many numbers are there from 400 to 700 in which the digit 6 occurs exactly twice?

Answer: Option A

From 400 to 500 = only 466
From 500 to 600 = only 566
From 600 to 700 ⇒ 606, 616, 626, 636, 646, 656, 676, 686, 696 and 660, 661, 662, 663, 664, 665, 667, 668, 669
Total numbers = 20