maths question

Question

Let (a,b,c,d) be an ordered quadruple of not necessarily distinct integers, each one of them in the set 0,1,2,3. For how many such quadruples is it true that a.d-b.d is odd? (for example, (0,3,1,1) is one such quadruple, because 0.1-3.1=0-3 is odd.)

Answer 1

The answer is 64 as shown in the  table below: