Answer:
 decrease of 64.3%
Step-by-step explanation:
Percentage change can be calculated from ...
 pct change = ((new value)/(original value) -1) × 100%
 = (50/140 -1) × 100%
 = (-9/14)×100% = -64 2/7% ≈ -64.3%
The price of crude fell about 64.3% in that period.