For each of the following stacking sequences found in FCC

For each of the following stacking sequences found in FCC metals, cite the type of planar defect that exists:
(a) . . . A B C A B C B A C B A . . .
(b) . . . A B C A B C B C A B C . . .
Now, copy the stacking sequences and indicate the position(s) of planar defect(s) with a vertical dashed line.