What is the best configuration to optimize performance on an Exchange server?

A.
Transaction logs andpagefile on same RAID 5, 10k rpm drives

B.
Pagefile and store groups on same RAID 1, 7.2 rpm group of spindles

C.
Store groups and transaction logs on different RAID 1 and RAID 5, 7.2k rpm drives

D.
Store groups and transaction logs on different arrays with 15k rpm drives