On the basis of part i) above, you know that Sus[0] >= Sus[t]fort >= 0.

Now look at the key ingredient of the model: Inf'[t] = a Sus[t] Inf[t] - b Inf[t] = (a Sus[t] - b) Inf[t].

Explain the statements: -> If Sus[0]

-> If Sus[0] > b/a, then the model predicts that the disease will spread and the infected population will increase until S[t] gets small enough that Sus[t] b/a, then an epidemic is in the cards.

On the basis of part i) above, you know that Sus[0)2 Susit] for t 20 Now look at the key ingredient of the model: Inf It] -a Sus[t] Inf[t]-b Inf [t] = (a Sus[t]-b) Inf[t] Explain the statements If Suso then the model predicts no epidemie because in this case Inf[t] goes down as t goes up. If Susto then the model predicts that the disease will spread and the infected population will increase until St) gets small enough that Sust] In other words, if Sus[0] >- , then an epidemic is in the cards