Response:
Personally, I would save up and pay for the computer. If I need the computer right away or for a good reason, yes I will use a credit card to buy the computer.
On the other hand, if I don't need it at the moment, I will save up to buy it later and would probably save anyway because it's easier than stacking up on my credit card depending on how much I use my credit card.
(This was a quickly made response, adjust it anyway you would like and if it doesn't fit the question than it is perfectly OK to not use it!)
“d”
you know b cannot work because the x is raised to the x^2 which would be a diff graph
a does not work because -x^3 the graph would be flipped
c is incorrect because the five is in the negative region; not positive