What are the conditions necessary to produce a reservoir for petroleum or natural gas?

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg

because if the tool that you are using is not balanced it there would be false mass.

answer///terminator or twilight zone;

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.