The solid is now a micropillar array with heights h of 2 m, diameters d of 5 m and center-to-center spacings l of 15 m (See schematic below). What is its roughness (real surface area divided by apparent surface area)? For your convenience, you can analyze a unit cell on the surface. (d) (0.25pt) For this micropillar array surface, assume that the solid material is hydrophobic and 0 = 120o. What is the apparent contact angle app