If z=sin(xy), x=5t, and y=2−t², what is dtdz using the chain rule? a) -10t cos (xy) b) -5cos (10t (2-t^2)) c) -5 cos (10t(2 - t^2)) - 4t sin(5t(2-t^2)) d) 10 cos(5t(2 - t^2)