You can
put this solution on YOUR website!every 5 minutes, the number of infected computers is MULTIPLIED by 20
__ 1...20...400...8000...etc __ how long until 100 million?
let t="time in minutes" __ 100M=1(20)^(t/5)
taking log __ log(100M)=(t/5)(log(20))
dividing by log(20) __ log(100M)/log(20)=t/5
multiplying by 5 __ 5[log(100M)/log(20)]=t