A fluid C is intended for use as a paint. To test its flow properties, fluid C of density 1 g/cm 3 is placed on a horizontal square tray of side length 1 m, at a uniform depth of d = 1 mm. The tray is then tilted at a sequence of angles, and it is found that flow of fluid C (driven by gravity) begins just when the tilt angle reaches 30 degrees from horizontal. Sketch the situation, in a 2D side view, at the onset of flow. What is the yield stress. To of fluid C?