$$\left. \begin{array} { l }
2 ^ { a } \cdot 3 ^ { b } \equiv 0 ( \bmod 12 ) \\
2 ^ { b } \cdot 3 ^ { a } \equiv 0 ( \bmod 27 )
\end{array} \right\}$$
For positive integers a and b that satisfy both congruences simultaneously, what is the minimum value of the sum $a + b$?
A) 3\\
B) 4\\
C) 5\\
D) 6\\
E) 7