Extracted text: A plank 10 ft long is placed in a horizontal position with its ends resting on two inclined planes, as showm in Fig. P- 530. The angle of friction is 20°. Determine how close the load P can be placed to each end before slipping impends. A MATHalino.com 10 ft 30° MATHalino.com 45° Figure P-530 B.