Table:
0
A
B
C
D
E
F
1
Class
Operator
No. Built
Year Built
Cars per Set
Unit nos.
2
Class 377/1
Southern
64
2002–2003
4
377101-164
3
Class 377/2
Southern
12
2003–2004
4
377201-206 377208-210 377213-215
4
Class 377/2
First Capital Connect
3
2003–2004
4
377207 377211-212
5
Class 377/3
Southern
28
2001–2002
3
377301-328
6
Class 377/4
Southern
75
2004–2005
4
377401-475
7
Class 377/5
First Capital Connect
23
2008–2009
4
377501-523
8
Class 377/6
Southern
26
2012-2014
5
377601-626
9
Class 377/7
Southern
8
2014
5
377701-708

Questions and formulas:
Question: What class has less than 12 numbers built operated by southern?
Formula: LET(query1,LET(query1,FILTER(A1:F1,B1="southern"),SUMMARIZE(CHOOSECOLS(query1,1),SUMX(CHOOSECOLS(query1,3)))),FILTER(query1,CHOOSECOLS(query1,2)<12))
Formula2: LET(query1,LET(query1,FILTER(A2:F9,B2:B9="southern"),SUMMARIZE(CHOOSECOLS(query1,1),SUMX(CHOOSECOLS(query1,3)))),FILTER(query1,CHOOSECOLS(query1,2)<12))
Level: hard