Problem 4. The wing on a Piper Cherokee general aviation aircraft is rectangular, with a span of 9.75 m and a chord of 1.6 m. The aircraft is flying at cruising speed (141 mi/h) at sea level. Assume that the skin friction drag on the wing can be approximated by the drag on a flat plate of the same dimensions. Note the standard sea level value of the dynamic coefficient of viscosity for air is µ = 1.7894 × 10-5 kg m.s' a) Calculate the skin friction drag for a completely laminar flow. (Round the final answer to one decimal place.) Hint: Remember that the wing has an upper and lower surface so you need to account for both. b) Calculate the boundary-layer thickness at the trailing edge for a completely laminar flow.