The enzyme Y catalyzes the elementary reaction AB-->A + B An enzyme concentration of 1.0M Y can convert a maximum

More AB - No change in the rate will happen because the substrate (reactants) are already in excess!

More B, More A - Adding more products will not affect the rate.

Inhibitor - Just from the name, 'in-hibit', it will decrease the rate because it tries to stop the reaction from happening.

More Y - In this case it will increase the rate of the reaction because AB is in excess for 1 M of Y. If the substrate (AB) weren't in excess, adding more Y wouldn't change anything.

Basically, here's some info that MasteringChemistry told me (I got this exact question):

An enzyme solution is saturated when all the active sites of the enzyme molecule are full. In this case, a 1.0 M Y solution is saturated when an AB concentration of 0.5 M or greater is present. When an enzyme solution is saturated, the reaction is occurring at the maximum rate.

The addition of more substrate to a solution that contains the appropriate enzyme will generally increase the rate of the reaction. However, if the enzyme is saturated the addition of more substrate will have no effect on the rate of reaction.
Also, the addition of more enzyme to a solution that contains the appropriate substrate will generally increase the rate of reaction as long as the substrate is in excess..