Write a Matlab user defined function based on the midpoint method for solution of an initial value problem. Test your solution with the model for fecal coliform die-off in a river given by : dc/dt = ? kc subject to the initial condition c(0) = 3,500 counts/100ml, where k = 0.15 day^-1 . Plot your result again analytical solution. Adjust time step size and check accuracy.