13.117. A cyclist traveled 60 km from point $A$ to point $B$. On the return trip, he rode the first hour at the same speed, then stopped for 20 minutes. Resuming his journey, he increased his speed by 4 km/h and therefore spent as much time traveling from $B$ to $A$ as he did traveling from $A$ to $B$. Determine the cyclist's speed on the trip from $A$ to $B$.