This (under age 2) child will be at your home from 3-10pm. Which means they take a full time day spot. So they would have to pay the day fee ($40) plus an additional hourly fee for your hours after closing. So I would charge $40 + $40 (4x10).

BUT...I would consider the fact this child is coming 2 days a week but pretty much making your under age 2 spot for the full week unusable by another family. So, if you REALLY want to move ahead with this I would strongly consider charging a lot more for potential lost wages for being unable to fill a full time spot they are potentially making an un-fillable part time spot.

All that said...I would NOT consider this if I was already working 7-6pm.