Answer
Binary search: max $12$ entries
Sequential search: max $4000$ entries
Work Step by Step
Binary search halves the input in every step hence it requires at max $⌈\log_2n⌉$ operations, while sequential search might need to check all entries hence requiring $n$ operations.
So for binary search in the worst case $⌈log2 4000⌉=12$ entries must be examined.
For sequential search $400$ entries should be inspected in the worst case.
