After hours care... need answer quick!

[planet.caravan67]

Hello, I have just set up an interview with someone today last minute, they need care 2 days a week from 3-10pm and other days regular hrs. my regular hours are 7-6 however I am having a hard time filling a spot and am willing to consider taking this client despite being outside business hours, my only question is how much would you charge? for under 2 (which child is) I am charging $40 a day, I was thinking $50 for this one does this sound fair? I would appreciate some advice, I have the interview in 2hrs!

UPDATE
I told them on the phone I wasn't sure if I would be able to do it and would have to speak with my husband before hand (you know, because I am not sure if he is going to be ok with an extra baby around the house when it's also his time off) anyhow they were able to come up a solution to their schedule and made 7pm the latest, however in my contract my close time is 5:30, they said drop off would be the earliest 2pm and latest 3pm. I don't really like those hours because from 1:30 to 3:30 is nap time and that is essentially my break and when I am able to do some stuff around the house, get dinner started, clean up from the morning, etc... however I really am quite in need of the money at the moment...

How much would you charge for such little hrs and late pick up? they asked if I do hourly rate, I did do it in the past but didn't like it and dodn't want to do it again

UPDATE 2
I am thinking $25 flat rate for 4hrs or less, and an additional $5 for every half hr after 6pm. that way it can be a little worth my while.... even if they left baby from 2pm the earliest time to 7pm the latest time they would still at most pay $35...