please help Matlab code would be very helpful

Infectious disease model The Kermack and McKendrick model is a simple infectious disease model that divides the population into three compartments. S is the susceptible (not yet infected) part of the population. I is the part that is currently infected and can spread the disease. R describes the population that has recovered and no longer spreads the disease. In this model, the dynamics of an epidemic is given by the following coupled, ordinary, first order, differential equations. = -asi, (1) d dt dI dt dR aSI - BI, (2) = BI, (3) dt where t is the time and a > 0 and B > 0 are parameters that define the model for a particular disease and population. The parameter a sets the transmission rate and depends on the number of contacts between people and the type of disease. The parameter B is the inverse of the length of time an infected individual can transmit the disease. For the first part of the work you will be using parameters: a = 3 x 10-4/day, B = 0.1/day, Ptot = 1000, Io = 10, So = Ptot 10, R0 = 0 where Ptot is the total population and Io, So, and Ro are the initial values of the population compartments. Please note that we are using days as the unit for time. (a) On paper: The sign of dI /dt determines if the number of infected is growing or decreas- ing; I(t) has a maximum or minimum when dI /dt = 0). Evaluate dI /dt = 0) in Eq (2) to find a condition for a maximum or mininum for the given parameters. On paper: Since the disease will grow only when dI /dt > 0, one defines a number, the so-called basic reproduction number, N, = Soa/B. If Nt > 1, the disease will become epidemic, for N,