YES(?, b + 3)

Initial complexity problem:
1:	T:
		(?, 1)    f4(a, b, c) -> f5(a, b, 1) [ 0 >= a /\ 0 >= b ]
		(1, 1)    f0(a, b, c) -> f2(a, b, 1) [ a >= 1 ]
		(?, 1)    f4(a, b, c) -> f4(a, b - 1, c) [ b >= 1 ]
		(1, 1)    f0(a, b, c) -> f4(a, b, 0) [ 0 >= a ]
	start location:	f0
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(?, 1)    f4(a, b, c) -> f4(a, b - 1, c) [ b >= 1 ]
		(1, 1)    f0(a, b, c) -> f4(a, b, 0) [ 0 >= a ]
	start location:	f0
	leaf cost:	2

A polynomial rank function with
	Pol(f4) = V_2
	Pol(f0) = V_2
orients all transitions weakly and the transition
	f4(a, b, c) -> f4(a, b - 1, c) [ b >= 1 ]
strictly and produces the following problem:
3:	T:
		(b, 1)    f4(a, b, c) -> f4(a, b - 1, c) [ b >= 1 ]
		(1, 1)    f0(a, b, c) -> f4(a, b, 0) [ 0 >= a ]
	start location:	f0
	leaf cost:	2

Complexity upper bound b + 3

Time: 0.090 sec (SMT: 0.086 sec)