Eighteen Across Two Pieces

Split [7, 2, 5, 10, 8] into 2 contiguous pieces so that the largest piece sum is as small as possible. Search over the answer: feasible(cap) walks left to right, starting a new piece whenever adding the next element would exceed cap, and reports whether the piece count is at most 2. Bounds start at lo = 10 (the largest element) and hi = 32 (the total).

step	lo	hi	mid	feasible(mid)	action
1	10	32	21	yes, pieces [7,2,5] and [10,8]	hi = 21
2	10	21	15	no, 3 pieces needed	lo = 16
3	16	21	18	yes	hi = 18

What is the final answer, and how many feasible calls does the search make in total?

21, after 3 calls

18, after 4 calls

18, after 3 calls

17, after 4 calls