Two sets of molecules are mixed into a system at time zero. After 10 seconds, equilibrium has been reached. At what time

[answerhappygod]

Two sets of molecules are mixed into a system at time zero.
After 10 seconds, equilibrium has been reached. At what time was
the entropy of the system maximal?
Prior to mixing of the two sets of molecules.
10 seconds (equilibrium).
Immediately upon mixing of the two sets of molecules.
The information given is not sufficient to pinpoint the
time.
5 seconds (half the time it takes to reach equilibrium)