9.8 is the gravitational field strength on earth, perhaps re-read the question
Answer:

Explanation:
To solve this problem we need to apply the concept related to Angular Acceleration. We can find it through the equation

Where for definition,

The number of revolution
was given by 20 times, then


We know as well that the salad rotates 6 more times, therefore in angle measurements that is

The cook at the end stop to spin, then using our first equation,

re-arrange to solve
,


We can know find the required time,

Re-arrange to find t, and considering that 



Therefore take for the salad spinner to come to rest is 3 seconds with acceleration of 
Magnetic field is produced by the magnet which will flow through any attractive item or even substance such as ferrofluid. Happy I could help:)
D is the answer! Hope it helps