In this problem we use the change of variables x = 5s + t, y = s - 2t to compute the integral ∫R(x + y) dA, where R is the parallelogram formed by (0, 0), (10, 2), (11, 0), and (1, -2). First find the magnitude of the Jacobian, |∂ (x, y) / ∂ (s, t)| =____________.