Help me build a water overflow controller in CPLD

[scorrpeio]

I want to build water overflow controller in cpld.
Plz tell me the logic for condition of truth table below

a b y(o/p)
0 0 1
1 0 1
1 1 0
1 0 0

Thank you in advance

 

[cydi]

project in vhdl

Your first and last logic levels seems contradictory! for a-b as 1-0, you hav output as 1 and 0 respectively.. i.e you have two outputs for same condition of inputs.. which is not logical at all! Are there any other conditions? Or are the inputs sequential?