He number, NN, of people who have heard a rumor spread by mass media by time, tt, is given by N\left(t\right)=a\left(1-e^{-kt}\ri ght)N ( t ) = a ( 1 − e − k t ). There are 6 million people in the population, who hear the rumor eventually. If 5% of them heard it on the first day, find the percentage of the population who have heard the rumor after 5 days.