Table:
0
A
B
C
D
E
F
1
payment id
settlement id
payment method code
date payment made
amount payment
payments
2
384
516
MasterCard
2018-02-16
241730
3
435
476
MasterCard
2017-05-28
448613
4
484
516
MasterCard
2017-06-24
456098
5
498
682
Discover Card
2017-08-06
38324
6
542
597
MasterCard
2018-01-10
407235
7
559
512
MasterCard
2018-02-18
235893
8
678
516
Visa
2017-12-16
459407
9
739
597
Discover Card
2017-10-07
71246
10
754
516
Visa
2018-02-24
7343
11
774
527
MasterCard
2018-01-28
319142
12
779
564
Visa
2017-05-28
155654
13
791
983
Visa
2017-05-03
172309
14
886
516
MasterCard
2017-07-31
423154
15
912
648
Discover Card
2017-05-04
123255
16
983
682
American Express
2018-01-19
177130

Questions and formulas:
Question: With which kind of payment method were the least number of payments processed?
Formula: TAKE(SORT(SUMMARIZE(C1,DCOUNTX(F1)), 2, 1), 1)
Formula2: TAKE(SORT(SUMMARIZE(C2:C16,DCOUNTX(F2:F16)), 2, 1), 1)
Level: hard
Question: Least used payment method.
Formula: TAKE(SORT(SUMMARIZE(C1,COUNTX(C1)), 2, 1), 1)
Formula2: TAKE(SORT(SUMMARIZE(C2:C16,COUNTX(C2:C16)), 2, 1), 1)
Level: hard