I am not to sure but I would go for B. identity.
280,706 is the standard form
It has to do with the number of dimensions you have in the figure. For example, in a square you have 2 dimensions, length and width. Since you have only two you use units^2. In a cube, you have 3 dimensions, length, width and height, which is where you get the units^3.
The equation for monthly payment is b = 49.05M.
<u>SOLUTION:</u>
Given, a cellular family phone plan cost $49 per minute plus five cents per minute of long distance service. We have to write an equation for the monthly payment b when M minutes of long distance service are used.
Now, given that,

<em>Equation:</em>
An equation is a statement that the values of two mathematical expressions are equal <em>(indicated by the sign =)</em>