11. In a set of real numbers a relation R is defined as x R y such that |x|+|y|, then relation R is (a) reflexive and symmetric but not transitive (b) symmetric but not transitive and reflexive (d) none of reflexive, symmetric and transitive (c) transitive but not symmetric and reflexive 12. If a, b and c are three mutually perpendicular unit vectors and d is a unit vector which makes equal angles with a, b and c then the value of a+b+c+d (a) 4+22 (b) 4+23 (c) 2+ 5 (d) 3+ 5 13. Let the area enclosed by the curve y = 1 - x and the line y = a, where 0a1, be represented by A(0) A(a). If k, then 1 A 2 3 (a) 1