The transition relation r0&!r1&!a | !r0&r1&a | r0&r1 is equivalent to r0&!a | r1&a:
r0&!r1&!a | !r0&r1&a | r0&r1
= (a ? r0&!r1&!1 | !r0&r1&1 | r0&r1 : r0&!r1&!0 | !r0&r1&0 | r0&r1)
= (a ? !r0&r1 | r0&r1 : r0&!r1 | r0&r1)
= (a ? (!r0|r0)&r1 : r0&(!r1|r1))
= (a ? r1 : r0)
= a&r1 | !a&r0