B. 100+10h is the correct expression to represent how much the landscaper charges.
Answer:

Step-by-step explanation:
The way I did this was I noticed that the graph had a y-intercept of 4 and the only exponential function that had a y-intercept of 4 was
Answer:
36.58% probability that one of the devices fail
Step-by-step explanation:
For each device, there are only two possible outcomes. Either it fails, or it does not fail. The probability of a device failling is independent of other devices. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
A total of 15 devices will be used.
This means that 
Assume that each device has a probability of 0.05 of failure during the course of the monitoring period.
This means that 
What is the probability that one of the devices fail?
This is 


36.58% probability that one of the devices fail
I = PRT
P = 8000
T = 4
R = 12%...turn to decimal...0.12
now we sub
I = (8000)(0.12)(4)
I = 3840 <==