 (a)Intrinsic conductivity=0.0224 s/cm
p_0=1.42e+011 /cm^3
(b)Since n_0>p_0, Conductivity=2.68 s/cm
With given acceptor impurity, 
n_0=1.42e+011 /cm^3
(c)Since p_0>n_0, Conductivity=1.27 s/cm 