Species Diversity + Calculus Probelm?

) Walker and Valentine (1984) suggested a model for species diversity which assumes that species extinction rates are independent of diversity but speciation rates are regulated by competition. Denoting the number of species at time t by N(t), the speciation rate by b, and the extinction rate by a, they used the... show more ) Walker and Valentine (1984) suggested a model for species diversity which assumes that species extinction rates are independent of diversity but speciation rates are regulated by competition. Denoting the number of species at time t by N(t), the speciation rate by b, and the extinction rate by a, they used the model

dN/dt= N[b(1-N/K)-a]

Find all equilibria under each condition ( Solving for N when dN/dt=0)

a) a<b
b)a>= b