The value of $$\,\int\limits_0^\infty {\int\limits_0^\infty {{e^{ - {x^2}}}{e^{ - {y^2}}}} dx\,dy\,\,\,\,} $$ is

Assume that the duration in minutes of a telephone conversation follows the exponential distribution $$\,f\left( x \right) = {1 \over 5}{e^{ - x/5}},\,x \ge 0.\,\,\,$$ The probability that the conversation will exceed five minutes is

Let $$j\, = \,\sqrt { - 1} $$. Then one value of $${j^j}$$ is

For the function $${{\sin z} \over {{z^3}}}$$ of a complex variable z, the point z = 0 is