The zombie apocalypse has finally occurred and the government estimates that the spread of the disease will have an infection rate of 0.1. Assuming that the population of the United States is about 300, 000, 000 the population of healthy people as a function of time in days is Phealthy = 300, 000, 000e −0.1t and the population of those either a zombie or dead is Pinf ected = 300, 000, 000(1 − e −0.1t ).