sql - Connect 2 queries -

i have 2 following queries:

select count(distinct custpersonid) count1    my_precustperson   rsv_no = 1510708         , custpersonid not null   select count(*) count2    my_precustperson   rsv_no = 1510708         , custpersonid null  

i want plus value count1 count2 (count1+count2) don't know how do. please me find out best query situation.

select (select count(distinct custpersonid) count1        my_precustperson       rsv_no = 1510708             , custpersonid not null)      + (select count(*) count2          my_precustperson         rsv_no = 1510708               , custpersonid null);