Availability smart contract

Pseudorandom selection

Random selection of experts is decided by relative weight of REP holdings. Before a smart contract is engaged, experts have the opportunity to stake REP tokens to signal their availability for work. These tokens are called availability stakes, and will be added as the chosen experts’ upvote bet on their evidence-of-work post. In this example the yellow star stops randomly along the bar, but is most likely to stop on the 2nd expert.

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Detail the algorithm...??