This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to estimate the amount of wallpaper needed
Calculate the area of the project.
Measure the length and height of each wall you wish to cover in wallpaper. Subtract doorways and large windows from the total length.

Pick from:
a). You can round the length measurement up to the nearest half foot or foot (or meter) to make it easier to calculate. Multiply the length and width of each wall to get the area in square feet.
b). Estimate the amount of blinds needed to cover the area once you've determined the length and height of each wall. This is to account for the area beyond the walk-in windows.
c). Your wall is the sole space you can cover with wallpaper. Measure the height, length, and a depth of approximately twelve inches, depending on the space needing.
d). Allow for an extra two feet or so in length to be easier. Decide how large of a wall you would like to cover.
The answer is:
a).