Monday he has 225 bars he sells 30 per day so subtract 30 to 225 and keep going till you get to friday tuesday 195 wednesday 165 thursday 135 friday 105 so on friday he will have 105 bars left
4 minutes= 240 seconds. So I did 240 seconds divided by 3 seconds (one copy is made in that time) then you get 80. I don't know if that explanation make sense but the math checks out.
