Answer:
Mass can never be negative. Everything has mass. Just like how they ask you to find area under the graph in maths. If the area is in the 3rd and 4th quadrant, when calculated, you would get negative answer.However, area can not be negative because it is a place/ location. It's exactly the same as mass.
You would have to run a little less than 2 blocks
Because many fuels are fossil fuels they take millions of years to form and the known reserves are being used much faster than the new ones being made