Given the parent functions f(x) = log10 x and g(x) = 3x - 1, what is f(x) g(x)?

Given the parent functions f(x) = log10 x and g(x) = 3x - 1, what is f(x) g(x)?

a. f(x) g(x) = log10 (3x - 1)x
b. f(x) g(x) = log10 x3x - 1
c. f(x) g(x) = 3x log10 x + log10 x
d. f(x) g(x) = log10 x - 3x log10 x