excel - SUM values based on date in date range in array -

i'm realy newbie in excel , need make advanced functions

i have excel (from google calendar) booking system

              b          c          12-01-2012  14-01-2012     8 13-01-2012  17-01-2012     11 15-01-2012  21-01-2012     3 

a - start date b - end date c - number of guests

now need sum number of guest days in year , find every days more 10 reservations.

for example, need return

 12-01-2012 - 08 guests  13-01-2012 - 19 guests  14-01-2012 - 19 guests  15-01-2012 - 14 guests 

may without creating large excel file days combinations? , how?

i'm working on excel 2013.

this can done quite using sumifs function. first need put each date in column d (set first date care manually, in d2 below, =d1+1 , copy down). count people each of days, put in e1 , drag down:

=sumifs(c:c, a:a, ">="&d1, b:b,"<="&d1) 

this sum passengers listed in column c (must formatted numbers, not text - looks might have text values in there), if row in column d (each day in year) within range of column & column b.

to find days larger 10 people, have column f (in f1 , dragged down) =e1>=10

this true if column e shows more 10 people day.