Which is an instrument on مِفْعَالٌ?

Six Derived Noun Types: Active/Passive Participles, Comparison, Instrument, Place/Time, and Ṣifah Mushabbahah

• مَكْتُوبٌ
• مِفْتَاحٌ
• أَكْبَرُ
• حَسَنٌ