Given the control system above I need to show that the characteristic equation is: $$5s^3+(25+K+5p)s^2+(25p+Kp+K)s+5K=0$$
I have used the block diagram reduction rules but I end up with an equation that looks like this: $$\frac{K}{(s+p)(k+5s+25)+K}$$
How would be the correct block diagram reduction process?