If $L^{-1}\left\{\frac{e^{-\pi s}}{s^2+4s+5}\right\} = \begin{cases} 0, & t \le \pi \\ e^{a(t-\pi)}(f(t)), & t>\pi \end{cases}$, then $f(\pi/2)=$
Consider the statements:I. If a series of positive terms is not convergent, then it is either divergent or oscillatory.II. In an alternating series, if $limn→∞∣un∣≠0\lim_{n \to \infty} |u_n| \neq 0$, then it is convergent.III. In a series of positive terms, if $limn→∞un=0\lim_{n \to \infty} u_n = 0$, then it may be convergent or divergent.IV. If $∑∣un∣\sum |u_n|$ is divergent and $∑un\sum u_n$ is convergent, then $∑un\sum u_n$ is conditionally convergent.
Which of the above statement(s) is(are) correct?
In large sample, the critical value for the single tailed test at 5% level of significance is?