I'll take a stab at this on a Thurs a.m. (without the rulebook open)

In (a) assume B accepts holding, we go back 10 to the B 28 DR then up 15 to the

B13 . As Piling on is a dead ball foul, there is no automatic 1D.But since we are repeating

the down we can apply the piling to see if A gets 1D.As they need to get to the 12,

its yards not gained so B 1D at the 13. If B declines the hold, B gets the ball at their own 1 1st down as the piling on is unrestricted and

turnover on downs stands.

In (B) if B takes the holding , back 10 to the A 21 3D repeated. Then we apply the piling on.

This is not a dual foul, so its A ball at the 6 and 1D due to dist gained as we are repeating the down.

If B declines the hold, we go up 15 to the 1 (unrestricted) and B 1D. A doesnt get the 1D for dist gained

due to the dead ball foul.

Am I close?