Use left factoring to resolve the pairwise disjointness problems in the following grammar: $A \rightarrow abc \ | \ ac \ | \ ab$

a) $A \rightarrow abcD \ | \ acD \ | \ abD$
b) $A \rightarrow abcD \ | \ acD \ | \ abC$
c) $A \rightarrow abc \ | \ ac \ | \ abD$
d) $A \rightarrow abc \ | \ ac \ | \ abC$