The amount of a fossil fuel that can be extracted at a profit using current technology is called what?

it has to be b, about 97 percent.

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west

3. dark matter

empty space could also be a simple vacuum