an engineer is working on determining the speed limit for a curved stretch of road. she knows the coefficient of friction between the wheels and the road is 0.7 when the road is dry and 0.3 when the road is wet. she also knows that the mass of the vehicle does not matter, but completes her calculations for a 700kg car. in order to set a speed limit that is safe under any conditions, should she perform her calculations with the coefficient of friction for wet or dry pavement?