One day while moving boxes you get tired and decide to use a rocket instead. You attach a small rocket of negligible mass to a 6.45 kg box. When you turn the rocket on, it provides a constant thrust of 212 N, and the sbox begins sliding across the pavement. If the magnitude of acceleration of the box is 17.0 m/s2, what is the coefficient of kinetic friction between the soapbox and pavement?