Algorithm: Resolution Time - ios

Question

I have an enquiry that needs to be resolved in fixed hour (Critical in 4hr, Important in 10hr and Normal in 24 hr). The enquiry res hours can be increased if there's a non working hour in between or a holiday. Non working can be full day or some hour in a specific day.
For eg: A critical enquiry raised at 08:02am on Monday should get resolved by 01:00pm
//Working hours of week
Mon 09:00am - 01:00pm
Tue Holiday
Wed 09:00am - 05:00pm(non working between 01:00pm - 02:00pm)
Thu 11:00am - 03:00pm(non working between 01:00pm - 02:00pm)
Fri 09:00am - 05:00pm(non working between 01:00pm - 02:00pm)
The inputs are enquiry type and enquiry log time. Output required is the resolution time.
My Approach:
Add all res hours to an enquiry as if all hrs are working. So, if log time is 08:02am for a critical enq add 4hrs i.e. 12:02pm as res time.
Enter while(true) loop where I check if next hr is a work time. If yes skip that hr else add that to res time and continue.
But this approach does not give me correct results when log time is non working.
NSDate *enqExpiration = nil;
int hoursNeededToCoverEnq = 0;
switch (enqType) {
case normalPriority:
hoursNeededToCoverEnq = lowResHours;
enqExpiration = [NSDate dateWithTimeInterval:lowResHours*hour sinceDate:capturedTime];
break;
case importantPriority:
hoursNeededToCoverEnq = mediumResHours;
enqExpiration = [NSDate dateWithTimeInterval:mediumResHours*hour sinceDate:capturedTime];
break;
case criticalPriority:
hoursNeededToCoverEnq = highResHours;
enqExpiration = [NSDate dateWithTimeInterval:highResHours*hour sinceDate:capturedTime];
break;
}
int aggregatedHrs = 0;
while(true){
capturedTime = [NSDate dateWithTimeInterval:1*hour sinceDate:capturedTime];
NSDateFormatter *dayFormat = [[NSDateFormatter alloc] init];
[dayFormat setTimeZone: [NSTimeZone timeZoneWithAbbreviation:#"GMT"]];
[dayFormat setDateFormat:#"EEEE"];
NSString* capturedDay = [dayFormat stringFromDate:capturedTime];
[dayFormat setDateFormat:#"dd/MM/yyyy"];
NSString* todayDate = [dayFormat stringFromDate:capturedTime];
if([weekends containsObject:capturedDay]){
enqExpiration = [NSDate dateWithTimeInterval:1*hour sinceDate:enqExpiration];
continue;
}else if([holidays containsObject:todayDate]){
enqExpiration = [NSDate dateWithTimeInterval:1*hour sinceDate:enqExpiration];
continue;
}else{
NSString *openTime, *closeTime;
for(int i=0; i<weekdaysTime.count; i++){
if([[((NSMutableDictionary*)[weekdaysTime objectAtIndex:i]) valueForKey:#"workingDay"] isEqualToString:capturedDay]){
openTime = [((NSMutableDictionary*)[weekdaysTime objectAtIndex:i]) valueForKey:#"openingTime"];
closeTime = [((NSMutableDictionary*)[weekdaysTime objectAtIndex:i]) valueForKey:#"closingTime"];
break;
}
}
NSDate *openTimeToday = nil, *closeTimeToday = nil;
[dayFormat setDateFormat:#"dd/MM/yyyy hh:mmaa"];
openTimeToday = [dayFormat dateFromString:[[todayDate stringByAppendingString:#" "] stringByAppendingString:openTime]];
closeTimeToday = [dayFormat dateFromString:[[todayDate stringByAppendingString:#" "] stringByAppendingString:closeTime]];
if([capturedTime compare:openTimeToday]==NSOrderedAscending || [capturedTime compare:closeTimeToday]==NSOrderedDescending ){
enqExpiration = [NSDate dateWithTimeInterval:1*hour sinceDate:enqExpiration];
continue;
}
}
aggregatedHrs ++;
if( aggregatedHrs == hoursNeededToCoverEnq )
break;
}
return enqExpiration;