Mass and weight are different. Mass is the measurement of how much matter an object has, while weight deals with the pull of gravity. For example, an astronaut floating in space is weightless, due to the limited influence of gravity. But he will still have mass, that is because mass and weight are different :)
For those seeking for the answer, its a source of electrical energy.
a = (V - V₀) / t = (14 - 4) / 10 = 10 / 10 = 1 m/s²