Through heat waves I'm pretty sure
Answer:
11.56521 m/s
Explanation:
= Area of first section = 
= Area of second section = 
= Velocity in first section = 1.9 m/s
= Velocity in second section
From the continuity equation we get

The speed of the river through the section of rapids is 11.56521 m/s
To show motion on a graph you draw the path of where the object has gone
The period is the reciprocal of the frequency. (1 divided by it)
Frequency = 261 / 1 second
Period = 1/261 second
= 0.00383... second (rounded)