multiply hours by dollars if hours are within certain range

Hi! I'm hoping someone can help me, please! I need to multiply the number of hours by a daily rate if the hours are 4 hours or more. and I need to multiply the number of hours by an hourly rate if the number of hours is 3 or less. I need it to round up to the next hour if the number of minutes is greater than 15. My formula is working great except for when the hours are 4 and the minutes are from 0 to 14 it wants to multiply by the daily rate. I'm thinking I need the hour qualifier in the beginning of the formula so that it will test if it is four hours and stop and not mess with the minutes? I tried to fix it and I ending up getting the daily rate when I had 3:16 minutes for example because it was rounding to 4. 3:16 minutes would only be the hourly rate because it wasn't actually greater than 4 hours. Any thoughts? Following is my formula:$A$83 is the daily rate and $A$84 is the hourly rate,
=IF(IF(MINUTE(AA3)<=14,HOUR(AA3),HOUR(AA3)+1)>4,$A$83,IF(MINUTE(AA3)<=14,HOUR(AA3),HOUR(AA3)+1)*$A$84)
I would greatly appreciate any help that could be offered.
Thanks again.
Angela