We study redundancy schemes, namely replication and erasure coding, used in Facebook photo storage.

C$)$ Suppose that f$4$ uses $($n$,$k$)=(12,8)$ within a cell and further uses $($n$,$k$)=(6,3)$ Reed Solomon coding across six cell. What is the redundancy factor. Show your derivations.

D$)$ Following Part $($C$),$ what is the minimum number of failed disks such that the data loss is irrecoverable? Show your derivations.