A. there will be 2000 bacteria after 40 hours.
B. there will be 8000 bacteria after 3 days. (might be wrong but i only calculated within my brain and this is how i did it) 3 days = 72 hours. we will exclude the 12 hours in 72 since it is unnecessary cause it will only double after 20 hours, so we have 60 hours left. 20 hours = 2000 another 20 = 4000 and the last 2000 hours is now 8000 since 4000 times 2 is 8000.