Consider a control system with the open loop transfer function given by :
$G_{OL}\left ( s \right )=\frac{K_{c}e^{-0.3z}}{1.5s+1}$
In the above function, pre-factor of $s$ is in minutes and $K_{c}$ is the gain of proportional controller. The frequency for phase margin of $30^{\circ}$ is $4.04$ rad/min. The value of $K_{c}$ for a gain margin of $1.7$ (up to one decinmal place) is _________________