a) 10% existential risk
b) 0% existential risk
* The "predictable power of AI" is very advanced predictive text. What a lot you can do with that, and there are clear limits.
* AI has no intent. The greedheads who find themselves in these positions of power have clear intent (often but not always bordering on and actively becoming misanthropic) put their intentions on AI - hence to doom mongering
* Who will starve with the failure of agriculture? A few, a lot, but not everybody. We are good at this - have been doing it a lot longer than computing or science
So yes, it very obviously is an extraordinary claim to say there is 0% existential risk.
I have a bridge to sell to anyone who believes a big claim without evidence.