There would be 5 groups of 4 and one left on the outside.
each group shakes hands with everyone else in their group, that makes 6 handshakes for each. 6x5=30 1 person from group A. shakes hands with everyone else and that makes 16 handshakes, 16x4=64 handshakes from group A.
From group B. one person goes around and that makes 12 more handshakes, 12x4=48 handshakes from group B. but they don't shake group A. because they already have.
A person from group C. then goes around and only shakes 8 peoples hand not including group A. or B. 8x4=32.
1 person from group D. shakes group E. hands and that makes 4 handshakes, 4x4=16 .
Group E. can no longer shake any groups hands because the groups have already shaken hands with them.
The outside person then shakes all the groups hand which is 20 handshakes.
64
48
32
16
20
=210
