YES(?, a + 2)

Initial complexity problem:
1:	T:
		(?, 1)    f2(a, b) -> f2(a - 1, b) [ a >= 2 ]
		(?, 1)    f2(a, b) -> f1(a - 1, c) [ 1 >= a ]
		(1, 1)    f300(a, b) -> f2(a, b)
	start location:	f300
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(?, 1)    f2(a, b) -> f2(a - 1, b) [ a >= 2 ]
		(1, 1)    f300(a, b) -> f2(a, b)
	start location:	f300
	leaf cost:	1

A polynomial rank function with
	Pol(f2) = V_1
	Pol(f300) = V_1
orients all transitions weakly and the transition
	f2(a, b) -> f2(a - 1, b) [ a >= 2 ]
strictly and produces the following problem:
3:	T:
		(a, 1)    f2(a, b) -> f2(a - 1, b) [ a >= 2 ]
		(1, 1)    f300(a, b) -> f2(a, b)
	start location:	f300
	leaf cost:	1

Complexity upper bound a + 2

Time: 0.079 sec (SMT: 0.076 sec)