The centerline of a new railway is to be set out along a valley. The first straight Al with azimuth 65∘, whilst the connecting straight IB with azimuth 125∘. Due to site conditions: 
a) The railway will have to be re-routed 
b) The azimuth of IB is incorrect 
c) The angle of intersection between Al and IB is 60∘60∘ 
d) Additional information is needed