If [tex]f(x) = -4x^{5} and g(x) = 10x^9 - 12x^4 + 6[/tex] (what is f x g) x?

A.) [tex]-40x^{14} + 48a^{3} x^{9} +6[/tex]
B.) [tex]40x^{14} - 12x^{4} + 6[/tex]
C.) [tex]-40x^{14} + 48x^{9} - 24x^{5}[/tex]
D.) [tex]-40x^{9} + 48x^{4} - 24[/tex]