Assured and contestable demand
So buyer wants 100 from incumbent, and 50 more.
First 100 are assured. 50 are contestable.
Cournot, bertrand mean entrant gets something
However rebates from incumbant blocks entrant.
eg reduce unit price for all if sales above certain amount
Compete on quality, features, on an axis. For example 2 shops in equilibrium are next to each other on road, to capture both on either side.
quality and price. everyone prefers high quality, but different preferences for tradeoff
different preferences for characteristics. eg car colour
Can have competing products.