A student riding a bicycle on a $5$ km one-way street takes $40$ minutes to reach home. The student stopped for $15$ minutes during this ride. $60$ vehicles overtook the student (assume the number of vehicles overtaken by the student is zero) during the ride and $45$ vehicles while the student stopped. The speed of vehicle stream on that road (in km/hr) is
- $7.5$
- $12$
- $40$
- $60$