The Gaussbot factory assembles robots. Each robot comes in one of three colours: red, blue, or green. Each robot also has a number stamped on its head: 1,2,3, or 4 . The nth robot assembled is the first robot to have the same colour and the same number as a previously assembled robot. What is the greatest possible value of n?
Answer Choices
A. 11
B. 12
C. 13
D. 7
E. 8