The base of an equilateral triangle is along the line given by $\;3x+4y=9\;$. If a vertex of the triangle is (1,2) , then the length of a side of the triangle is :

Question

$(a)\;\large\frac{2 \sqrt{3}}{15}\qquad(b)\;\large\frac{4 \sqrt{3}}{15}\qquad(c)\;\large\frac{4 \sqrt{3}}{5}\qquad(d)\;\large\frac{2 \sqrt{3}}{5}$