Liver Implant Assist Device

While testing the energy generated by a liver implant assist device, Diana lost her research data because of computer crash. She saw a work formula on a piece of paper and wonders if this is the work function of the device.

What is known:

• The expression of the liver implant assist device is
  w(t) = 17 - 15t + 9t² - t³
• The unit for work, power and time is mJ (mil-Joules), mw (mil-watts), and year respectively.
• The liver implant assist device needs to have positive energy generating rate (power) when the device starts to work.

• Using test for monotonic functions to find the functions increasing interval.
• The derivative of the energy function is energy generating rate (power).