Suppose r contains a reference to a new rectangle(5, 10, 20, 30). which of the fol­lowing assignments is legal? (look inside the api documentation to check which interfaces the rectangle class implements.) a. rectangle a = r; e. measurable e = r; b. shape b = r; f. serializable f = r; c. string c = r; g. object g = r; d. actionlistener d = r;