Answer:
C5 and its absolute configuration is R
Explanation:
A chiral center is a carbon atom (C) which is bonded to four different groups, generating optical activity in the molecule.
The first two chiral centers are:
The thrid chiral center is C5, which is bonded to H, the above C and its CH3, the carbon chain (seen from left to right) and the carbon chain (seen fron rigth to left).
The absolute configuration of it is R (clockwise)