$(1-2y)\;(1+3x+9x^2+27x^3+81x^4+243x^5+729x^6)$ = $(1-64y^6)$, $(y\;\neq\;1)$, then $\frac{x}{y}$ is

Question

$(a)\;\frac{3}{2}\qquad(b)\;\frac{2}{3}\qquad(c)\;\frac{4}{9}\qquad(d)\;\frac{9}{4}$