Answer:
b) 7.00
Explanation:
N( t ) = -20( t - 5 )²
dN/ dt = -20 x 2 ( t - 5 )
For maximum N ( depth )
dN/dt = 0
- 40 ( t - 5 ) = 0
t = 5
So at 2 + 5 = 7 .00 am depth of water reaches its maximum.
To solve this problem we will apply the concept of wavelength, which warns that this is equivalent to the relationship between the speed of the air (in this case in through the air) and the frequency of that wave. The air is in standard conditions so we have the relation,
Frequency 
Speed of sound in air 
The definition of wavelength is,

Here,
v = Velocity
f = Frequency
Replacing,


Therefore the wavelength of that tone in air at standard conditions is 0.589m
Accelerated motion such as a vehicle (car) or a moving item such as a (football thrown in the air)