At the instant shown, cars A and B travel at speeds of 70 mi/h and 50 mi/h, respectively....

At the instant shown, cars A and B travel at speeds of 70 mi/h and 50 mi/h, respectively. If B is decreasing its speed at 1400 mi/h2 while A is increasing its speed at 800 mi/h2, determine the acceleration of B with respect to A. Car B moves along a curve having a radius of curvature of 0.7 mi.