Table:
0
A
B
C
D
E
1
State (class)
Vacator
Reason for change
Successor
Date of successor's formal installation
2
Georgia (2)
Richard Russell, Jr. (D)
Died January 21, 1971
David H. Gambrell (D)
February 1, 1971
3
Vermont (1)
Winston L. Prouty (R)
Died September 10, 1971
Robert Stafford (R)
September 16, 1971
4
Louisiana (2)
Allen J. Ellender (D)
Died July 27, 1972
Elaine S. Edwards (D)
August 1, 1972
5
Georgia (2)
David H. Gambrell (D)
Successor elected November 7, 1972
Sam Nunn (D)
November 7, 1972
6
Louisiana (2)
Elaine S. Edwards (D)
Successor elected November 13, 1972
Bennett Johnston, Jr. (D)
November 14, 1972

Questions and formulas:
Question: Who is the vacator for the February 1, 1971 date of successor's formal installation?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,E1="february 1, 1971"),2))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E6,E2:E6="february 1, 1971"),2))
Level: medium
Question: What is the state of the senator with a November 14, 1972 date of successor's formal installation?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,E1="november 14, 1972"),1))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E6,E2:E6="november 14, 1972"),1))
Level: medium