Problem Specification: a) Technique: This practical problem is based on Camera Calibration. b) Input: Photos of your pen. c) Output: Real length of your pen. d) Problem: You may need to use your webcam/mobile camera to take photos of your pen, and you need to find out the real length of the pen (which you must measure on millimeter scale beforehand as ground truth). You may use any programming language, and any calibration technique to solve this problem.