Problem 19E

In someone infected with measles, the virus level N measured in number of infected cells per mL of blood plasma reaches a peak density at about t=12 days when a rash appears and then decreases fairly rapidly as a result of immune response. The area under the graph of Nt from t = 0 to t = 12 as shown in the figure is equal to the total amount of infection needed to develop symptoms measured in density of infected cells time. The function N has been modeled by the function f(t)=t(t21)(t+1) Use this model with six subintervals and their midpoints to estimate the total amount of infection needed to develop symptoms of measles.

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