Same setup. Speed of current = ?

• a$\dfrac{x}{2}\left(\dfrac{1}{t_2} - \dfrac{1}{t_1}\right)$
• b$\dfrac{x}{2}\left(\dfrac{1}{t_1} + \dfrac{1}{t_2}\right)$
• c$\dfrac{x}{2}\left(\dfrac{1}{t_1} - \dfrac{1}{t_2}\right)$
• d$x(t_1 - t_2)$