1 00:00:00,000 --> 00:00:06,000 One way of solving this is to find out which terms appear in several places-- 2 00:00:06,000 --> 00:00:13,000 for instance, this one--the number of persons taken from the susceptible to the exposed compartment 3 00:00:13,000 --> 00:00:18,000 and then the number of persons taken from the exposed to the infectious compartment, 4 00:00:18,000 --> 00:00:23,000 and the number of persons taken from the infectious to the recovered compartment. 5 00:00:23,000 --> 00:00:27,000 If you write it like that, it's easier to read and you can immediately see 6 00:00:27,000 --> 00:00:29,000 that the total number is conserved. 7 00:00:29,000 --> 00:00:36,000 The number of persons we lose here we gain here, the number of persons we lose here we gain here, 8 00:00:36,000 --> 00:00:39,000 and the number of persons we lose here is gain here. 9 00:00:39,000 --> 00:00:45,000 So up to very tiny round off errors of the total number and result you'll see that the infection 10 00:00:45,000 --> 00:00:47,000 takes quite some time to evolve. 11 00:00:47,000 --> 00:00:52,000 The maximum of the exposed compartment comes first and then comes 12 00:00:52,000 --> 00:00:57,000 the maximum of the infectious compartment, and as we go, you'll see that the number of 13 00:00:57,000 --> 00:00:59,000 susceptible persons shrinks drastically 14 00:00:59,000 --> 99:59:59,999 and the number of recovered persons grows by the same amount.