Which expression is equivalent to 3x(-4x^2+5x-8)-6(x^2-5x+7)?

A. 12x^3-9x^2+6x-42
B.-12x^3-54x^2+6x-42
C.-12x^3+9x^2+6x-42
D.-27x^3-6x^2+6x-42