((a)) The debtor may modify the plan at any time before confirmation, but may not modify the plan so that the plan as modified fails to meet the requirements of .

((b)) After the debtor files a modification under this section, the plan as modified becomes the plan.

((c)) Any holder of a secured claim that has accepted or rejected the plan is deemed to have accepted or rejected, as the case may be, the plan as modified, unless the modification provides for a change in the rights of such holder from what such rights were under the plan before modification, and such holder changes such holder’s previous acceptance or rejection.