Solve the challenge

Offering extra earnings. It is necessary to organize non-stop traffic through four side intersections.
Dano.
Crossroads with entrances to it No. 1,2,3 and 4
The width of the roadway is 12 meters on each side.
The journey opens in turns (1, 2, 3, and 4) only on one side for 15 seconds.
And 15 seconds, the driveway is closed from all sides. The pedestrian passage is open.
The full cycle is 75 seconds.
The maximum speed of travel through the intersection is 20 km / h
Minimum speed at the entrance to the intersection 5 km / h
For 200 meters in front of the intersection, the site is divided into 4 parts of 50 meters.
It is necessary to calculate the speed of the cars at each of the 4 sites when approaching the crossroads with each of the
4 sides so that the cars do not stand in front of the intersection.
What formulas to use, how to calculate, what methods to apply better I do not know.
What ideas? I'll consider all options.
The cost of the task?