Answer
m is negative,
b is positive.
Work Step by Step
$(0,b)$ is the point of intersection of the line $y=mx+b$
with the vertical axis (T=0).
When T=0,... b is positive, the y-intercept is above the origin.
Moving $\Delta x=10$ (+10 units to the right), $\Delta y$ becomes negative, so
$ m=\displaystyle \frac{\Delta y}{\Delta x}\qquad$ is negative.
