Venn Diagrams

In a 3-circle Venn diagram with A, B, C: if n(A only) = 20, n(B only) = 15, n(C only) = 10, n(A intersect B only) = 8, n(A intersect C only) = 6, n(B intersect C only) = 5, and n(A intersect B intersect C) = 3, what is n(A union B union C)?