Table:
0
A
B
C
D
E
1
District
Vacator
Reason for change
Successor
Date successor seated
2
Georgia 9th
Vacant
Rep-elect Garnett McMillan died before taking seat
Benjamin H. Hill (D)
May 5, 1875
3
Massachusetts 1st
James Buffington (R)
Died March 7, 1875
William W. Crapo (R)
November 2, 1875
4
Oregon At-large
George A. La Dow (D)
Died May 1, 1875
Lafayette Lane (D)
October 25, 1875
5
Tennessee 4th
Samuel M. Fite (D)
Died October 23, 1875
Haywood Y. Riddle (D)
December 14, 1875
6
Connecticut 3rd
Henry H. Starkweather (R)
Died January 28, 1876
John T. Wait (R)
April 12, 1876
7
Florida 2nd
Josiah T. Walls (R)
Lost contested election April 19, 1876
Jesse J. Finley (D)
April 19, 1876
8
Illinois 3rd
Charles B. Farwell (R)
Lost contested election May 6, 1876
John V. Le Moyne (D)
May 6, 1876
9
Louisiana 5th
Frank Morey (R)
Lost contested election June 8, 1876
William B. Spencer (D)
June 8, 1876
10
Idaho Territory At-large
Thomas W. Bennett) (I)
Lost contested election June 23, 1876
Stephen S. Fenn (D)
June 23, 1876
11
Kentucky 5th
Edward Y. Parsons (D)
Died July 18, 1876
Henry Watterson (D)
August 12, 1876
12
South Carolina 2nd
Edmund W. M. Mackey (IR)
Seat declared vacant July 19, 1876
Charles W. Buttz (R)
November 7, 1876
13
Massachusetts 4th
Rufus S. Frost (R)
Lost contested election July 28, 1876
Josiah G. Abbott (D)
July 28, 1876
14
Colorado Territory At-large
Thomas M. Patterson (D)
Colorado admitted to the Union August 1, 1876
Statehood achieved
Statehood achieved
15
Indiana 3rd
Michael C. Kerr (D)
Died August 19, 1876
Nathan T. Carr (D)
December 15, 1876

Questions and formulas:
Question: what is the total number of reasons for change where the date the successor was seated is june 8, 1876?
Formula: ROWS(UNIQUE(FILTER(C1, E1="June 8, 1876")))
Formula2: ROWS(UNIQUE(FILTER(C2:C15, E2:E15="June 8, 1876")))
Level: medium
Question: what is the reason for change where the date the successor was seated was july 28, 1876?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,E1="July 28, 1876"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E15,E2:E15="July 28, 1876"),3))
Level: medium
Question: what is the district where the vacator is vacant?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1="Vacant"),1))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E15,B2:B15="Vacant"),1))
Level: medium