Add Columns Based on Multiple Flag Columns

[EnglishManBob]

I need to add up a data column (Members) flagged by multiple columns (Year1, Year2, Year3) for each date. 

What solution would use the fewest tools?

Input Table

Date	Members	Year1	Year2	Year3
1-Jan	1	0	0	1
1-Jan	1	0	0	1
1-Jan	1	0	1	0
1-Jan	1	0	1	0
1-Jan	1	1	0	0
1-Jan	1	1	0	0
1-Jan	1	1	0	0
1-Jan	1	1	0	0
1-Feb	1	0	0	1
1-Feb	1	0	0	1
1-Feb	1	0	1	0
1-Feb	1	1	1	0
1-Feb	1	1	0	0
1-Feb	1	1	0	0
1-Mar	1	0	1	1
1-Mar	1	0	1	0
1-Mar	1	1	1	0
1-Mar	1	1	1	0
1-Mar	1	1	0	0
1-Mar	1	1	0	0
1-Apr	0	1	1	0
1-Apr	0	1	1	0
1-Apr	1	1	0	0
1-Apr	1	1	1	0
1-Apr	1	1	1	0

Sum members for Year1, for 1-Jan, 1 + 1 + 1 + 1 = 4.

Sum Members for Year1, for 1-Feb, 1 + 1 + 1 = 3.

Sum Members for Year1, for 1-Mar, 1 + 1 + 1 + 1 = 4.

Sum Members for Year1 (Note the flag variable rules out 2), for 1-Apr, 1 + 1 + 1 =3.

Output Table

Date	MemberYear1	MemberYear2	MemberYear3
1-Jan	4	2	2
1-Feb	3	2	2
1-Mar	4	4	1
1-Apr	3	2	0

[mattnason1 · Accepted solution]

Here's how I did it.

[Qiu · Accepted solution]

@EnglishManBob 
 A little different appoach.