a)
well done
b)
well, a function for a relationship means, the x-coordinates must not repeat in a set, namely that for every "y" there must be a unique "x" coordinate, no X-REPEATS.
so for example in a relation that say is { (3, 4) , (5, 4) , (7, 4) , (10, 11) }, we do have y-coordinates repeated, but for a function that doesn't matter, our x-coordinates are not repeated thus, it's a function.
in this case, let's see the relationship set, just a few points { (3,5) , (3,6) , (3,8) , (6,10)}, well darn, we have 3 repeated three times in the x-coordinate slots, therefore is not a function, just a relation.
