conversations.from: human
conversations.value: There was a big sale on cat food at the pet store. 20 people bought cat food that day. The first 8 customers bought 3 cases each. The next four customers bought 2 cases each. The last 8 customers of the day only bought 1 case each. How many cases of cat food were sold?
  Solve this problem.
conversations.from: assistant
conversations.value: The first 8 customers bought 8*3=24 cases
  The next 4 customers bought 4*2=8 cases
  The last 8 customers bought 8*1=8
  In total 24+8+8=40 cases were sold