Let $X=\{ a, b, c, d \}$.
Given the belief measure $Bel(\{b\})= 0.1 , Bel(\{a,b\})= 0.2, Bel(\{b,c\}) = 0.3, Bel(\{b,d\})=1$ , determine the coresponding basic assignment.
I'm trying to use the formula $m(A) = \Sigma_{B \in P(A)} (-1)^{|A-B|}. Bel(B)$ to try to calculate the $m(.)$ values. But I don't understand how I can calculate, say, $m(\{a\})$ without knowing what $Bel(\{a\})$ is.