What is a line of an object that acts as a reference line for dimensioning called?

Two microscope slides are placed horizontally, one on top of the other, with a drop of a dishwashing liquid between them. the gap between the slides is 1 mm. a machine pulls the top slide to the right with a velocity of 0.15 millimeters per second while the bottom slide is held stationary. a stress gage indicates that a shearing stress of 0.5 pa is required to pull the top slide with this velocity. if the dishwashing liquid adheres to both slides during this process, what is the viscosity of the liquid? specify whether your answer is dynamic or kinematic viscosity, and use appropriate units.