For any three positive real numbers a, b and c, $9(25a^2+b^2) +25(c^2−3ac)=15b(3a+c)$. Then

Question

$\begin{array}{1 1} \text{(1) b, c and a are in A.P.} \\ \text{(2) a, b and c are in A.P.} \\ \text{(3) a, b and c are in G.P.} \\ \text{(4) b, c and a are in G.P.} \end{array}$