Hi there!
a.
To find the total amount of people that have ENTERED by t = 20, we must take the integral of the appropriate function.

Evaluate using a calculator:

b.
To solve, we can find the total amount of people that have entered of the interval and subtract the total amount of people that have left from this value.
In other terms:

We can evaluate using a calculator (math-9 on T1-84):


c.
If:

Then:

Evaluate at t = 20:


This means that at t = 20, there is a <u>NET DECREASE</u> of people at the movie theater of around 20.823 (21) people per hour.
d.
To find the maximum, we must use the first-derivative test.
Set S(t) - R(t) equal to 0:

Graph the function with a graphing calculator and set the function equal to y = 0:
According to the graph, the graph of the first derivative changes from POSITIVE to NEGATIVE at t ≈ 17.78 hours, so there is a MAXIMUM at this value.
<u>Thus, at t = 17.78 hours, the amount of people at the movie theater is a MAXIMUM.</u>
a = your total price before the coupon and sales tax.
b = your coupon's given discount (for example, 25% off)
c = your discounted total
(a - (ab)) = c
c + (.075c) = your answer.
With some numbers plugged in:
a = 50$, b = -25%
50 - (50 x .25)
50 - 12.5 = 37.50$
37.5 + (37.5 x .075)
37.5 + 2.82* = 40.32$
So you would have to pay $40.32
What? Is this a serious question?
Answer:
Global life expectancy is the average age that people live to be. This is not a national life expectancy where we look only at one country and is on a global level. The industrial revolution impacted life expectancy by raising wages, living conditions. New technology was invented and many breakthroughs in sanitation were made.