This problem is an example of what is called two-sided non-compliance (see Gerber and Green (2012), Ch.
ບັນຫານີ້ເປັນຕົວຢ່າງຂອງສິ່ງທີ່ເອີ້ນວ່າຫນຶ່ງຂ້າງບໍ່ປະຕິບັດຕາມເປັນ (ເບິ່ງ Gerber and Green (2012), Ch.