If the function $f(x) = 2x^3 - 9 ax^2 + 12 a^2x + 1$, where $a>0$, attains its maximum and minimum at $p$ and $q$ respectively such that $p^2 = q$, then $a$ equals :

Question

( A ) 2
( B ) 1/2
( C ) 1
( D ) 3