Switch Open,Switch Closed

Electricity and Magnetism Level 2

A battery has an EMF (Electromotive Force ) of $\displaystyle 6\text{ V}$ and an internal resistance of $\displaystyle 0.4 \ Ω$ . It is connected to a $\displaystyle 2.6\ Ω$ resistor through a SPST (single pole, single throw) switch.

Find the potential difference between the terminals of the battery when the switch is open and when the switch is closed, in volts.