what does the downward slop of ppc indicates?
The downward slope of PPC shows for the production of every additional unit of one good, more and more units of other good has to be sacrificed. This is known as Marginal Rate of Transformation (MRT) or Opportunity Cost.
It should be noted that as we move down along the PPC, the slope of PPC (or MRT) increases. This suggests that as the production increases, to produce each additional unit of one good, more and more units of other good needs to be sacrificed. In other words, the opportunity cost increases.
there exist a negative relation between the production of robot and pizza as the resources are limited if more amount of pizza is produced lesser amount of robot can only be produced and this is the reason for the downward slope of the ppc
the above statement proves why ppc is concave