A capacitance (C = 50F) is charged to potential difference of 20V. the charging battery is disconnected and the capacitor is connected to another cell

A capacitance (C = 50µF) is charged to potential difference of 20V. the charging battery is disconnected and the capacitor is connected to another cell of emf 10V, with the opposite plate of capacitor joined with the (+) ve terminal of cell. Find the charge flown through 10V cell :-

 (1) 250 µC 

(2) 500 µC

 (3) 750 µC 

(4) 1000 µC