Root Locus Problem

Root Locus Problem
Problem RLocus13

Here is the transfer function for a system to control.

G(s) = 4(s + 0.5)/(s³ + 11s² + 25.25s + 65.25)

This open loop system has three poles: -1 + j2.5, -1 - j2.5, -9
The open loop system has one zero: -0.5
The system is being controlled in a feedback system as shown above at the right.

Here is the root locus for the system.

Determine the gain, K, that will produce the minimum overshoot in the system by finding the gain for the largest damping ratio in the complex roots.
Estimate where the third pole is for the gain found in the first part.