Convert from electronvolt to arroba [Spain]

Unit Definition (electronvolt)
The electronvolt is a unit of mass used in particle physics. Mass and energy are related by Einstein's famous equation, E = mc². The constant c is the speed of light, 299.79 x 10E6 m/sec. An energy of 1 electronvolt is therefore equivalent to a mass of about 1.782 662 x 10E-33 gram, or about 1.073 544 x 10E-9 atomic mass unit.

Unit Definition (arroba [Spain])
The arroba [Spain] is a traditional unit of weight in Spain and Portugal, equal to 1/4 quintal. However, the Spanish and Portuguese quintals are of different sizes. In Spain, the arroba equals 25.36 pounds (11.50 kilograms); arrobas of very similar sizes were established in the Spanish speaking countries of Latin America. The arroba has also been used as a metric unit equal to exactly 15 kilograms. The name of the unit comes from ar rub', Arabic for "the quarter."