If the set $$x$$ contains 7 elements and set $$y$$ contains 8 elements, then the number of bijections from $$x$$ to $$y$$ is

If the middle term of the AP is 300, then the sum of its first 51 terms is

If the sum of $$n$$ terms of an AP is given by $$S_n=n^2+n$$, then the common difference of the $$\mathrm{AP}$$ is

The third term of a GP is 9. The product of its first five terms is