Answer
(a) $1,100 per year
(b) Last 3 years
(c) 1994, 2004
Work Step by Step
(a) The median income in 1999 was about 47.6, and about 41.5 in 1993.
\frac{47.6 - 41.5}{1999 - 1993} \approx 1.1, or $1,100 per year
(b) If you look from 1996 to 1999, you can see that the slope is somewhat steeper than in the 3 years prior, indicating greater increase in income over the same time period.
(c) Look for "valleys" in the graph, and then at the year where the curve begins to increase again.