Which comparison of قُلْتُ, بِعْتُ and خِفْتُ is correct?

Hollow Verbs: Seven Iʿlāl Rules and Three Short Paradigms

• Original yāʾ drops in all three
• All begin with ḍammah
• خِفْتُ is yāʾ-hollow
• Qultu: wāw/ḍammah; biʿtu: yāʾ/kasrah; khiftu: wāw/kasrah