If $i = \sqrt{-1}$ then $\left[i^{18} + \left(\dfrac{1}{i}\right)^{25}\right]^3 =$

The number of permutations of the letters of the word INSTITUTION are .......

If $x + y = \dfrac{\pi}{4}$, then $(1 + \tan x)(1 + \tan y) =$

A straight line makes equal negative intercepts on the coordinate axes. If the perpendicular distance from the origin to the line is 4 units, then the equation of the line is ......