YES(?, a + 3)

Initial complexity problem:
1:	T:
		(?, 1)    f5(a, b) -> f5(a - 1, b) [ a >= 1 ]
		(?, 1)    f5(a, b) -> f1(a, c) [ 0 >= a ]
		(1, 1)    f300(a, b) -> f5(a - 1, b) [ a >= 1 ]
		(1, 1)    f300(a, b) -> f1(a, c) [ 0 >= a ]
	start location:	f300
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(?, 1)    f5(a, b) -> f5(a - 1, b) [ a >= 1 ]
		(1, 1)    f300(a, b) -> f5(a - 1, b) [ a >= 1 ]
	start location:	f300
	leaf cost:	2

A polynomial rank function with
	Pol(f5) = V_1
	Pol(f300) = V_1
orients all transitions weakly and the transition
	f5(a, b) -> f5(a - 1, b) [ a >= 1 ]
strictly and produces the following problem:
3:	T:
		(a, 1)    f5(a, b) -> f5(a - 1, b) [ a >= 1 ]
		(1, 1)    f300(a, b) -> f5(a - 1, b) [ a >= 1 ]
	start location:	f300
	leaf cost:	2

Complexity upper bound a + 3

Time: 0.119 sec (SMT: 0.115 sec)