[填空题]
A squirrel is climbingpbrx3a9xm q7 +rb +o6o6s9pcga tree with velocity $v \mathrm{~ms}^{-1}$ for 9 seconds. This is shown in the graph below.
1. Write down the squirrel's velocity at t=4 .
V(4)= m/s
2. Find the squirrel's acceleration at t=2 .
m= m/s
3. Find the total distance travelled by the squirrel.
d= m