11. A grain of dust of mass 0.04 g carries a charge of -3.0 nC (n = nano = 10-9). The grain starts at rest at point A inside an electric field (not shown) and reaches point B with a speed of 5.0 cm/s. The electric potential at A is -50 V. A B a) Is the potential at B higher or lower than at A? Explain how you know before doing any math. b) Calculate the electric potential at point B.