The values of c for which the function f(x) is a p.d.f. is?
\(f\left( x \right) = \left\{ {\begin{array}{*{20}{c}} {\frac{c}{{\sqrt x }},}&{0 < x < 4}\\ {0,}&{otherwise} \end{array}} \right.\)
1
\(\frac{1}{2}\)
2
\(\frac{1}{3}\)
3
\(\frac{1}{4}\)
4
\(\frac{1}{6}\)