Four EDGE timeslots per cell gives a total of 12 extra abis timeslots.
But then you will have to subtract 12 from iii), before you find the abis capacity for the voice.
Total Number of TCHs =132-12 = 120
Total number of Abis timeslots for voice =120*1/4 = 30
Therefore, total Number of Abis timeslot needed for the site = 30+9+12 = 51
No, the BCCH and SDCCH don’t need a separate resource on the abis. They form part of the signalling, which I included in the calculation.