if possible, go earlier

• mom → school (20 min + 10 min margin)
  • monday: 08:40
  • tuesday: 09:15
  • wednesday: 08:05
  • thursday: 10:10
  • friday: 07:55
• dad → school (30 min + 10 min margin)
  • monday: 08:30
  • tuesday: 09:05
  • wednesday: 07:55
  • thursday: 10:00
  • friday: 07:45