Changing multiplier based on cell value

Hi!

I'm creating a registration form where you state which days you have attended an activity. The participant receives 4 points for attending on Saturdays and 6 points for Sundays. When they has attended more than seven Saturdays and/or Sundays, they receive 5 points for Saturdays and 7 points for Sundays. This shall not affect the points awarded for attending the first seven Saturdays or Sundays.

A number one is put in column B for participation on that date and in column C the calculation should be. There will be one sheet per month in addition to a summary sheet where you can see the total.

Attachment 885097

Can anyone please help me?