When 2.0x10^-16 kg of matter is converted into energy how much energy is released

Matter and energy are directly proportional. We know this from the Einstein's equation E=mc², where E is energy, m is mass and c is the speed of light, c=3*10^16 m/s. So lets input the numbers:

E = (2*10^-16) * (3*10^8) ² = (2*10^-16) * (9*10^16) = (2*9) * 10^0=18 J. So the correct answer is E=18 J.