If $\log _ { e } a , \log _ { e } b , \log _ { e } c$ are in an $A . P$. and $\log _ { e } a - \log _ { e } 2 b , \log _ { e } 2 b - \log _ { e } 3 c , \log _ { e } 3 c - \log _ { e } a$ are also in an $A . P$. , then $a : b : c$ is equal to\\
(1) $9 : 6 : 4$\\
(2) $16 : 4 : 1$\\
(3) $25 : 10 : 4$\\
(4) $6 : 3 : 2$