Suggest a poka-yoke device for each of the following and indicate whether the device is of the warning or control type.
a. Filling an automobile crankcase with the correct amount of oil
b. Ensuring that the polarity is not crossed on an electrical connection
c. Doing a preflight check on an aircraft
d. Detecting a weak battery in a smoke detector
e. Keeping a coffeepot from overheating
f. Ensuring that DVDs are properly inserted into DVD recorders.