A binary search tree contains the value 1, 2, 3, 4, 5, 6, 7, 8. The tree is traversed in pre-order and the values are printed out. Which of the following sequences is a valid output?

For a database relation $$R(a,b,c,d),$$ where the domains of $$a, b, c, d$$ include only atomic values, only the following functional dependencies and those that can be inferred from them hold:
$$a \to c\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,b \to d$$
This relation is

Let $$R (a, b, c)$$ and $$S(d, e, f)$$ be two relations in which $$d$$ is the foreign key of $$S$$ that refers to the primary key of $$R.$$ Consider the following four operations $$R$$ and $$S$$
(a) Insert into $$R$$ (b) Insert into $$S$$
(c) Delete from $$R$$ (d) Delete from $$S$

Which of the following statements is true about the referential integrity constraint above?

Given $$\sqrt {\left( {224} \right),} = {\left( {13} \right)_r},$$
The value of the radix' $$r$$ is: