NFHS Punt doesn't cross NZ

[FredFan7]

Fourth and 10 for K from their own 20 yard line. K in punt formation. Snap sails over punter's head and into the end zone. Punter recovers, scrambles, and as he's being tackled gets off an extremely weak punt. It rolls to K's own 15 where;
a) R muffs it, K recovers and advances to K's 31 yard line.
b) K recovers and advances to K's own 19 yard line.
c) The ball comes to rest at the 15 with no one attempting to recover it.

What's your call? NFHS rules.