2a's got to do with Euler's Formula and the fact that:
2q = r*(no. edges in each region) > r*(length of shortest cycle)
im a little confused i used Euler's formula and i got that the number of faces should be 9 which is clearly a lot less than it is in real life...is there any way i can work out the number of actual faces by looking at the graph? and also, where did u get the other formula from? and how do i calculate the number of edges in each region?