Issues:

• Incorrect Turn Condition: The condition used to pop points while building the upper hull is wrong (it keeps right turns instead of left turns).
• Incorrect Lower Hull Logic: The loop structure and point access used to build the lower hull are fundamentally flawed and do not follow the algorithm's requirements.
• Naive Merging: The upper and lower hulls are simply concatenated, which likely results in duplicated start/end points in the final hull list.

Test Example:

Testing with these set of points gives us incorrect results:

{0, 0}, {4, 0}, {4, 4}, {0, 4}, {2, 2}

Expected : 16 ( Square of side 4 )
Got : 13.6569