Use the concept of beat frequency to find the applicable final freqeuncy for 20Hz beat frequency.
Beat can be defined as 'the interference pattern between two sounds of slightly different frequencies0
The expression for beat frequency is given as

Where,
Final frequency
Initial frequency
The beat frequency for us is 25Hz and the initial frequency is 240Hz, then

Being an absolute value, two values are possible, both in addition and subtraction:

The two possible values are


Answer:
Jolt can expect to replace 160 units.
Explanation:
given data:
standard deviation 1.7
average lfe of connectors = 18.2 months
number of connectors = 5000

z(19) = 0.4706
P(x< 19) = P(z< 0.4706)
P(x< 19) = 0.6810 from z table
therefore 68.1% fails within 19 months.
hence 0.3190 {100-68.1} will fail during that period.
number of unit of Jolt that need to be replace, on average is 0.319*500 = 160 units.
My guess is; The warmer ocean adds water vapor to the air mass.
I'm really sorry if I'm wrong
Hot air has a lower density than the surrounding atmosphere, therefore,it will rise.. The reason it is "cold" in the upper atmosphere is actually because of a lower air density.