Answer:
1.when it is closest to the sun
2.when it is midway between its farthest
Explanation:
According to the law of Kepler's
T ² ∝ r³
T=Time period
r=semi major axis
We also know that time period T given as

v=Speed







So we can say that ,when r is more then the speed will be minimum and when r is low then speed will be maximum.
To solve this problem we need to use the proportional relationships between density, mass and volume, together with Newton's second law.
The force can be described as

Where,
m = Mass
g = Gravitational acceleration
At the same time the Density can be defined as

Where,
m = mass
V = Volume
Replacing the value of the mass at the equation of Force we have,

Since the difference between the two forces gives us the total Force then we have to

Where
Force of the water
= Force of plastic
Therefore with the values for this force we have,





Therefore the tension in the thread is 16.412N