conversations.from: human
conversations.value: Since 1989, Lily has treated herself to 1 hydrangea plant, each year.  Each plant costs $20.00.  By 2021, how much money has Lily spent on hydrangeas?
  Give me a clear explanation.
conversations.from: assistant
conversations.value: She started buying plants in 1989 and it's now 2021 so she has bought these plants for 2021-1989 = 32 years
  Each plant costs $20.00 and she has bought them for 32 years so she has spent 20*32 = $640.00 on hydrangeas