If the function $f(x) = \left\{ \begin{array}{l l} 3ax+b & \quad for \quad x > 1 \\ 11 & \quad for \quad x = 1 \\ 5ax-2b & \quad for \quad x < 1 \end{array} \right.$ is continuous at $x=1$.find the values of a and b .
$\begin{array}{1 1}(A)\;a=4\;b=2 \\(B)\;a=3\;b=2 \\(C)\;a=0\;b=1 \\(D)\;a=3\;b=6 \end{array}$