bid
open override fun bid(vehicle: FleetVehicle, cfp: CallForProposals, space: FleetSpaceIfc): Bid?(source)
Return
the vehicle's offer, lower being better, or null to decline. Declining is normal operation and not an error: a vehicle out of range, out of charge, or already committed has nothing useful to say, and a dispatcher that received a bid from it anyway would have to invent a number meaning "no", which is how sentinel values get compared as though they were costs.