For the following polynomial, determine the values of K for which the roots have a negative real part:

s⁵ + s⁴ + 3s³ + 2s² + s + K

a) K > 0.618
b) 0 < K < 0.618
c) 0.618 < K < 1.6
d) 0 < K < 1.6
e) No value of K exists