If two adjacent sides of a regular, 6-sided die have the values $a$ and $b$ when viewed side-on and read left-to-right, the value on the top of the die is given by $3(a^3b - ab^3)\mod 7$.
Determine the value on the top of the die if (a) $a=2, b=6$, (b) $a=3, b=5$.
Using Python's operators:
>>> a = 2
>>> b = 6
>>> 3 * (a**3 * b - a * b**3) % 7
3
>>> a = 3
>>> b = 5
>>> 3 * (a**3 * b - a * b**3) % 7
1