Match the reactions in Column I with appropriate types of steps/reactive intermediate involved in these reactions as given in Column II :

	Column I		Column II
(A)		(P)	Nucleophilic substitution
(B)		(Q)	Electrophilic substitution
(C)		(R)	Dehydration
(D)		(S)	Nucleophilic
		(T)	Carbanion

The number of distinct real roots of $${x^4} - 4{x^3} + 12{x^2} + x - 1 = 0$$

Let $$\omega = {e^{{{i\pi } \over 3}}}$$, and a, b, c, x, y, z be non-zero complex numbers such that
$$a + b + c = x$$
$$a + b\omega + c{\omega ^2} = y$$
$$a + b{\omega ^2} + c\omega = z$$

Then the value of $${{{{\left| x \right|}^2} + {{\left| y \right|}^2} + {{\left| z \right|}^2}} \over {{{\left| a \right|}^2} + {{\left| b \right|}^2} + {{\left| c \right|}^2}}}$$ is

A value of $$b$$ for which the equations $$$\matrix{ {{x^2} + bx - 1 = 0} \cr {{x^2} + x + b = 0} \cr } $$$

have one root in common is