Table:
0
A
B
C
D
E
1
State (class)
Vacator
Reason for change
Successor
Date of successors formal installation
2
Georgia (2)
James Jackson (DR)
Resigned sometime in 1795
George Walton (F)
Appointed November 16, 1795
3
Connecticut (1)
Oliver Ellsworth (F)
Resigned March 8, 1796
James Hillhouse (F)
Elected March 12, 1796
4
Massachusetts (2)
Caleb Strong (F)
Resigned June 1, 1796
Theodore Sedgwick (F)
Elected June 11, 1796
5
Massachusetts (1)
George Cabot (F)
Resigned June 9, 1796
Benjamin Goodhue (F)
Elected June 11, 1796
6
Connecticut (3)
Jonathan Trumbull, Jr. (F)
Resigned June 10, 1796
Uriah Tracy (F)
Elected October 13, 1796
7
Tennessee (1)
New seat
Tennessee was admitted to the Union
William Cocke (DR)
Elected August 2, 1796
8
Tennessee (2)
New seat
Tennessee was admitted to the Union
William Blount (DR)
Elected August 2, 1796
9
Vermont (1)
Moses Robinson (DR)
Resigned October 15, 1796
Isaac Tichenor (F)
Elected October 18, 1796
10
Maryland (1)
Richard Potts (F)
Resigned October 24, 1796
John E. Howard (F)
Elected November 30, 1796
11
South Carolina (2)
Pierce Butler (DR)
Resigned October 25, 1796
John Hunter (DR)
Elected December 8, 1796

Questions and formulas:
Question: Why did the change happened in Massachusetts (2)?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Massachusetts (2)"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E11,A2:A11="Massachusetts (2)"),3))
Level: medium
Question: How many different reasons are there for the change in Connecticut (3)?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Connecticut (3)"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E11,A2:A11="Connecticut (3)"),3))
Level: medium