Let R be a relation from A to B and S be a relation from B to C.
(a) Prove that Dom (S ? R) ⊆ Dom (R) .
(b) Show by example that Dom (S ? R) = Dom (R) may be false.
(c) Which of these two statements must be true:
Rng(S) ⊆ Rng(S ? R) or Rng(S ? R) ⊆ Rng(S)?
Give an example to show that the other statement may be false.
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