Basic Excel command

SUMIF
SUMIF(range, criteria, [sum_range])
https://support.office.com/en-ca/article/SUMIF-function-169b8c99-c05c-4483-a712-1697a653039b

Others:
http://www.excelfunctions.net/Basic-Excel.html
http://www.gcflearnfree.org/excel2010/10