The constat rate is given by the slope of the line. By definition, the slope of the line is defined as follows:
[tex]m\text{ = }\frac{Y2-Y1}{X2-X1}[/tex]
Where (X1,Y1) and (X2,Y2) are given points on the line. In our case, for example, we can take the points:
(X2,Y2) =(4,50)
(X1,Y1)=(2,70)
Replacing the previous data in the equation of the slope we obtain:
[tex]rate=m\text{ = }\frac{Y2-Y1}{X2-X1}=\frac{50-70}{4-2}=\frac{-20}{2}\text{ =-10 ft/s}[/tex]
Then, we can conclude that the constant rate is
-10 ft /s : a descent of 10 ft per second.
