4.19 A force P parallel to a surface inclined 35 above the horizontal acts on an 18-lb block initially at rest on the surface (see Fig. 4.31). If the coefficients of friction for the block and surface are s=0.32 and k=0.24, (a) for what range of values of P will the block remain at rest? (b) what is the acceleration of the block if P=16lb ? (c) what is the acceleration of the block if P=4.0lb ? 19. (a) 5.6lbP15 (c) 5.0ft/s2 down th Figure 4.31 Problem 4.19 27. (a) 0P49N; (b) ( (c) 1.7im/s2