YES(?, 3)

Initial complexity problem:
1:	T:
		(1, 1)    start(a) -> a(a) [ a >= 1 ]
		(1, 1)    start(a) -> a(a) [ a >= 2 ]
		(1, 1)    start(a) -> a(a) [ a >= 4 ]
		(?, 1)    a(a) -> a(a*b) [ 1 >= 2*b /\ 3*b >= 2 /\ a >= 2 ]
	start location:	start
	leaf cost:	0

Testing for unsatisfiable constraints removes the following transition from problem 1:
	a(a) -> a(a*b) [ 1 >= 2*b /\ 3*b >= 2 /\ a >= 2 ]
We thus obtain the following problem:
2:	T:
		(1, 1)    start(a) -> a(a) [ a >= 1 ]
		(1, 1)    start(a) -> a(a) [ a >= 2 ]
		(1, 1)    start(a) -> a(a) [ a >= 4 ]
	start location:	start
	leaf cost:	0

Complexity upper bound 3

Time: 0.031 sec (SMT: 0.030 sec)