Why do we need to define both an assi 4. The population P(t) of a fishery at time t can be given by: = P(5 – P) – 6.25, P(0) = Po. (a) What is the equilibrium solution, i.e. P when = 0? (b) Create a phase portrait and sketch representative curves. (C) Based on the phase portrait, for what values of P, will the population go extinct, i.e. reach 0 in finite time?