Just add them up 15+5+3+8
Answer:
Option D [
] in the list of possible answers
Step-by-step explanation:
For this problem you are supposed to use a calculator that allows you to do an exponential regression. There are many tools that can help you with that, depending on what your instructors has assigned for your class.
I am showing you the results of a graphing tool I use, and which after entering the x-values and the y-values in independent "List" forms, when I request the exponential regression to fit the data, I get what you can see in the attached image.
Notice that the exponential of best fit with my calculator comes in the form:

with optimized parameters:

Notice as well that since:

the exponential best fit can also be written:

and this expression is very close to the last option shown in your list of possible answers
If he does three hours, its 9 strips, for four, its 12, six is 18, seven is 21, and nine is 27