Answer: 20.4 miles
Explanation:
Here we need to use the equation:
Velocity = Distance/Time.
Initially we have that he can travel 30 miles in 2 hours, so the velocity is:
V = 30mi/2h = 15mph
Now, we reduce the velocity by 3 mph, so the new velocity is 15mph - 3 mph = 12mph.
Now we want to know the distance traveled in 1.7 hours with this velocity, this is.
Velocity*Time = Distance
12mi/h*1.7h = 20.4 miles
To solve this problem it is necessary to apply the concepts related to the capacitance in the disks, the difference of the potential and the load in the disc.
The capacitance can be expressed in terms of the Area, the permeability constant and the diameter:

Where,
= Permeability constant
A = Cross-sectional Area
d = Diameter
Potential difference between the two disks,
V = Ed
Where,
E = Electric field
d = diameter
Q = Charge on the disk equal to 
Through the value found and the expression given for capacitance and potential, we can define the electric charge as





Re-arranging the equation to find the diameter of the disks, the equation will be:

Replacing,


Therefore the diameter of the disks is 0.03m
Here it is given that initial speed of the package will be same as speed of the helicopter

displacement of the package as it is dropped on ground

acceleration is due to gravity

now by kinematics



by solving above equation we have

so it will take 5.2 s to reach the ground