Which tank will fill first?

Fill The Tank Riddle

3rd and 4th.Let us break down the problem into 5 steps.1. The water in tank1 will get filled up to the connectivity of tank1 and the tank2 and then it will start flowing to tank2.2. The water in tank2 will get filled up to the connectivity of tank2 and the -tank3 and then it will start flowing to tank3.3. The water in tank3 will get filled up to the connectivity of tank2 and the tank3 and then it will start flowing to tank3.4. As the outlet of tank3 and inlet of tank4 are not at the same level, water will continue to fill tank3 till the inlet of tank4.5. Now both the tank3 and tank4 fill simultaneously until both fill together.