The accompanying figure shows the plot of distance fallen versus time for an object that fell from the lunar landing module a distance $80 \mathrm{m}$ to the surface of the moon. (FIGURE CAN'T COPY)
a. Estimate the slopes of the secant lines $P Q_{1}, P Q_{2}, P Q_{3},$ and $P Q_{4},$ arranging them in a table like the one in Figure 2.6
b. About how fast was the object going when it hit the surface?