Total Inductance in transformer

Just a simple question, usually we can determine the sign of the mutual inductance M by seeing the position of the dots (as the current enters through it). But if you see the upper picture, we don't have any dots. How to determine if it's -M or +M from the arrows?

• Suppose that I put the dot at the head of the arrow, I got $M_{lm}, -M_{lr}, M_{ml}, -M_{mr}, M_{rl}, -M_{rm}$ but the correct answer, everything is positive. Is this a wrong concept of my understanding? Aug 15, 2016 at 16:00
• Sorry, you get $M_{lm}$ etc for what? And "the correct answer" to what question? Aug 15, 2016 at 16:09
• What is the question about the circuit in the first picture that is supposed to have the answer $M_{lm}$, etc.? Aug 15, 2016 at 16:21
• I asked to calculate the total inductance, and this picture has the correct answer as $L = L_l+L_m+Lr+2M_{lm}+2M_{mr}+2M_{lr}$. But in other cases, I also found the equation like this $L = L_l+L_m+Lr-2M_{lm}-2M_{mr}-2M_{lr}$. So, I'm confused how to determine the sign of M, which will affects my calculations later... Aug 15, 2016 at 16:28