What is the opportunity cost of producing 1 comb at point M as production moves from point N to point M

The table below shows the tradeoff between different combinations of brushes and combs that might be produced in a year with the limited capacity for Country X, ceteris paribus.

Combinations Number of Brushes Number of Combs
J ,0 ,4
K ,10, 3
L ,17 ,2
M ,21 ,1
N ,23 ,0

Does the data support the law of increasing opportunity cost?
C) Given the data, what do you expect to be the shape of the Production Possibilities curve?