Find the Degree of the Polynomial Function $$f ( x ) = 18 x ^ { 5 } + 4 x ^ { 4 } - 9$$

Find the degree of the polynomial function.
- $$f ( x ) = 18 x ^ { 5 } + 4 x ^ { 4 } - 9$$

A) 5
B) 4
C) 10
D) 18