Bic 4 color pen in a psychological horror movie

A new psychological horror movie, the same old Bic pen doing a great detective work.

Lee Harker an FBI agent is looking for a serial killer. For detective work and organizing clues she's using the Bic 4 colors.

How much lead do you actually use

 A little bit of math to calculate how much of the lead is actually used and ends up on the page or better said how much is wasted away during sharpening.

A very shor explination from SteveMould