The figure shows how the terminal potential difference $V$ of a cell changes with the current $I$ drawn from it. The line passes through the two marked points. The cell is then joined to a variable resistor, which is adjusted until the power dissipated in the resistor is as large as it can be. What is that largest power?

Fig. 1: A graph of the terminal voltage V of a cell, in volts, on the vertical axis against the current I drawn from it, in amperes, on the horizontal axis. A straight line slopes down from a point marked 12 V on the vertical axis, where the current is zero, through a second marked point at 2.0 A and 8.0 V, and on to the right. Dashed lines run from the two marked points to the axes.