Answer
The slope has unit: billions of dollars per year
The net income has grown by $5$ billion each successive year.
Work Step by Step
The unit of N is billions of dollars,
the unit of t is years (after 2000)
The slope has unit: billions of dollars per year
In the model found in part (a), $N=5t-30$,
the slope equals $+5.$
Interpretation:
The net income has grown by $5$ billion each successive year.
