c# LINQ) How to sum between dates in a DataTable? :     Name           issue_date      free_coupon_days category
    Einstein       25/Dec/2015           60          movie 
    Hellen Keller  01/Jan/2016            7          movie
    Einstein       09/Jul/1999            9          movie
    Einstein       14/Jun/2015            3          waterpark
    Hellen Keller  19/Nov/1980           30          movie
    Einstein       29/Sep/2015           19          movie

I have a DataTable dt, for example.

And I want to sum free_coupon_days with criteria as 'Eienstein', Date between '25/Sep/2015 ~ 25/Dec/2015', 'movie'.

The desirable output is **79** as calculated the rows as below.

    Name           issue_date      free_coupon_days category    
    Einstein       25/Dec/2015           60          movie
    Einstein       29/Sep/2015           19          movie

I've tried some ways But I'm beginner against complicated conditions.
How can I do this in LINQ ?

I always respect excellent people here.
Thank you so much ! 