Four vehicles are traveling on a 4-kilometer circular track. The four vehicles are traveling at constant speeds of 46 km/h, 61 km/hr, 62 km/hr, and 70 km/hr, respectively. Assume you are an observer standing at a point on the track for a period of 30 minutes and are recording the instantaneous speed of each vehicle as it crosses your point.  What is the space-mean speed for this stream of traffic?

Round your answers to the nearest 2 decimal points in km/h. Note: Only include the numerical value (e.g. 51.36)