Answer:
D.
b = 175; which is the initial # of pages to start
Step-by-step explanation:
you can find the slope to find b or y-intercept (x=0) for equation
y=mx+b
to find m = (y2-y1)/(x2-x1)
(x1,y1) = (9, 100)
(x2, y2) = (15, 50)
m = (50-100) / (15-9) = -50/6 = -25/3
let use point (15, 50)
y=mx+b
50 = -25/3*x + b
50 = (-25/3)*(15) + b
50 = -125 + b
b = 175; which is the initial # of pages to start
Another triple integral. We're integrating over the interior of the sphere

Let's do the outer integral over z. z stays within the sphere so it goes from -2 to 2.
For the middle integral we have

x is the inner integral so at this point we conservatively say its zero. That means y goes from
and 
Similarly the inner integral x goes between 
So we rewrite the integral

Let's work on the inner one,

There's no z in the integrand, so we treat it as a constant.

So the middle integral is
I gotta go so I'll stop here, sorry.
The down payment is $248
The total amount of monthly payments is 62