In this question we reconsider the si epidemic model allowing the infectious contact rate to be a function of time. the model equations are di = -bsi s(0) = si, i (0) = ii, 8si b = bo (1.5 +1.4 cos (356)] (a) consider the equation y= a + b cos (wt). what is the physical meaning of the parameters a, b, and 12? (b) in our definition of the infectious contact rate what is the significance of the term 27/365? (c) why might the infectiour contact rate vary in a periodic manner? (d) plot b/bo as a function of time. (e) reduce the system of equations to a single differential equation for the rate of change of the number of susceptibles in the population. solve this differential equation to find the number of susceptibles as a function of time. express your answer in terms of the initial number of infectives in the population - not the initial number of susceptibles in the population. (f) consider the parameter values li = 200, k = 30,000 individuals, bo = 0.4 x 10-6 individuals - 1 day-1. (i) plot the number of susceptibles as a function of time (0