With sector forwarding, bad blocks are mapped to successive sectors in the spare sectors area.

Assume that block $15$ fails and is mapped to spare $1.$ Next, block $10$ fails and is mapped to spare $2.$

$($a$)$

How many revolutions are needed to sequentially access all sectors on the track?

$($b$)$

How many revolutions would be needed for the same task if block $10$ failed before block $15?$

$($c$)$

How many revolutions would be needed for the same task if sector slipping were used instead of sector forwarding?