i (31) {0:051:36 W\"): 1 2 10;(t6) for6

10 cos(+) for 0 S t S 6 Ht 6) 2 for 6 < t S 10 The depth of a river at a certain point is modeled by the function VV defined above, where W (t) is measured in feet and time t is measured in hours. (a) Find W' (8). Using correct units, explain the meaning of W' (8) in the context of the problem. (b) The graph of W is concave down for 3 t < 3.5. Use the line tangent to the graph of W att = 3 to show that W (3.5) 9. (c) Find lim t 92