$(1)$Give $"logn"$ Sorted lists each of size $"\frac{n}{logn}",$what is the total time required to merge them into one single list?

$(2)"n"$ strings each of length $"n"$ are given them, what is the time taken to sort them,$2-$way merge?

$(3)$The median of "n" elements can be found in $O(n)$ time.Which one of the following is correct about the complexity of quicksort,in which the median is selected as pivot?

$(4)$In quicksort,for sorting $'n'$ elements,the $\frac{n}{4}th$ smallest element is selected as pivot using $O(n)$ time algorithm.What is the worst case time complexity of quicksort?