1. The slope of a velocity curve is acceleration. The slope is negative, but is not constant. The 2nd choice would be better:
... changing negative acceleration
2. 1.5 hours is 1.5×3600 = 5400 seconds, so the change in velocity over that time will be
... 12 m/s² × 5400 s = 64,800 m/s = 6.48×10⁴ m/s
Adding that value to the initial velocity gives
... 2.39×10⁴ m/s + 6.48×10⁴ m/s = 8.87×10⁴ m/s
as the final velocity. Your choice is correct.
