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