Table 5.9 shows the upward vertical velocity v(t), in ft/min, of a small plane at time t seconds during a short flight.
(a) When is the plane going up? Going down?
(b) If the airport is located 110 ft above sea level, estimate the maximum altitude the plane reaches during the flight.

Table 5.9 v(t) t v(1) 0 10 100 -140 10 20 110 -180 20 60 120 0 30 490 130 -820 40 890 140 -1270 50 980 150 -780 60 830 160 -940 70 970 170 -540 80 300 180 -230 90 10 190 0