Q64. The sum of the coefficient of $x ^ { 2 / 3 }$ and $x ^ { - 2 / 5 }$ in the binomial expansion of $\left( x ^ { 2 / 3 } + \frac { 1 } { 2 } x ^ { - 2 / 5 } \right) ^ { 9 }$ is\\ (1) $21 / 4$\\ (2) $63 / 16$\\ (3) $19 / 4$\\ (4) $69 / 16$