conversations.from: human
conversations.value: Lauren wanted to make burgers and fries for dinner.  She needed a few things from the grocery store and bought the following:  2 pounds of hamburger meat that was on sale for $3.50 a pound.  1 pack of hamburger buns for $1.50.  A head of lettuce for $1.00 and a large 1.5-pound tomato that was priced at $2.00 per pound.  She also needed a jar of pickles that cost $2.50 and she had a $1.00 off coupon for that item.  How much change would Lauren get back if she paid with a $20 bill?
  How to solve this?
conversations.from: assistant
conversations.value: She bought 2 pounds of hamburger meat at $3.50 per pound so 2*3.50 = $7.00
  The tomato weighed 1.5 pounds and cost $2.00 per pound so 1.5*2 = $3.00
  When you add up all her items she spent 7+1.50+1+3+2.50=$15.00
  Her items added up to $15.00 and she had a $1.00 coupon off pickles so 15-1 = $14.00
  She paid with a $20.00 bill so 20-14 = $6.00 in change