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how to calculate total resistance in circuit with parallel and series resistors connected

A battery of EMF 8.0 V and internal resistance r = 1.0 – is connected to an external circuit as shown:

http://i.stack.imgur.com/jL7HM.png

I need to find out the total resistence and my problem is that I dont know which resistors consider parallel and which are in series as there is connection for 3ohm resistor after 1st resistor which confuses me. Answer I got is that the total resistance is 15ohms could anyone confirm it? Or point out where I went wrong?