Answer:
a)
Step-by-step explanation:
The initial speed, u = 0 m/s (The boat starts from rest)
Th final speed, v = 7 m/s
The time, t = 15 s
To find the average acceleration, use the equation below

The acceleration of the boat is in the direction of the motion
b) If the boat continues with the same acceleration for another 6 seconds:
Total time, t = 6 + 15 = 21 s
Speed = Acceration x time
Speed = 0.47 x 21
Speed = 9.87 m/s