Calculating EMF (2 Viewers)

[healthnut]

I have a really difficult time with physics and now we're doing circuits ah!!!

Here's the question:

When switch S in the figure is open, the voltmeter V of the battery reads 3.09

. When the switch is closed, the voltmeter reading drops to 2.99

, and the ammeter A reads 1.61

. Assume that the two meters are ideal, so they do not affect the circuit.

Find emf

.

I have absolutely NO IDEA how to calculate the emf!!!! Someone please help me understand how to complete this question!!!!