Given: Total marbles = 30, each student gets between 5 and 10 marbles, all different.

A and C got odd marbles. B and D got even marbles.

A > B, C > D, and B > D.

Step 1: Possible distinct sets (5 to 10) with sum 30:

{5, 6, 9, 10}, {5, 7, 8, 10}, {6, 7, 8, 9}

Step 2: Check parity and conditions:

In {6, 7, 8, 9}:
Evens: 6, 8 → B > D ⇒ B = 8, D = 6
Odds: 7, 9 → A > B ⇒ A = 9, C = 7

Verify:

A > B ⇒ 9 > 8 ✔
C > D ⇒ 7 > 6 ✔
B > D ⇒ 8 > 6 ✔

Final Distribution:

A = 9, B = 8, C = 7, D = 6

mean(B,C,D)=$\dfrac{8+7+6}{3}$=7