What is the color of person A's cap?

Puzzle Of the day.

I already posted 2 puzzles on my blog.  You can find them here – Puzzles.  Here is another puzzle on the list from my side.  For answers you can contact me on mangal.pardeshi@indiamvps.net .

In a small village in the middle of nowhere, a dacoit caught three persons A, B & C. One day, the crazy dacoit takes them out and places them in a line on three chairs, in such a way that person C can see both person A and person B, person B can see only person A, and person A can see none of the other persons. The dacoit shows them 5 caps, 2 of which are black and 3 of which are white. After this, he blindfolds all the 3 persons, places one cap on each of their heads, and removes the blindfolds again. The dacoit tells these three persons that if any one of them is able to determine the color of his cap within one minute, all of them are released. Otherwise, they will all be executed. None of the persons can see his own cap, and all are intelligent. After 59 seconds, person A shouts out the (correct) color of his cap!

The Question: What is the color of person A's cap, and how does he know?