If functions f(x) and g(x) are continuous in [a, b] and differentiable in (a, b) then which of the following is correct if there exists at least one point c, a < c < b, such that ( begin{vmatrix}f(a) & f(b) g(a) & g(b) end {vmatrix} )?

• A. (b + a) ( begin{vmatrix}f(a) & f (c) g(a) & g (c) end {vmatrix} )
• B. (b a) ( begin{vmatrix}f(a) & f (c) g(a) & g (c) end {vmatrix} )
• C. (b + a) ( begin{vmatrix}f(a) & f'(c) g(a) & g'(c) end {vmatrix} )
• D. (b a) ( begin{vmatrix}f(a) & f'(c) g(a) & g'(c) end {vmatrix} )