TIaO - Part 4

Jeremy can control the flow of water in the inlets of a specific tank. The tank has $2$ inlets. The first inlet can fill the tank in $4$ hours. The second inlet can fill the tank in $12$ hours.

He controlled the flow by the following steps:

• First, he made the first inlet flow.
• When the tank was filled by $\frac{1}{4}$ by the first inlet, he turned off the first inlet and turned on the second inlet.
• When the tank was filled by $\frac{1}{4}$ by the second inlet, he turned off the second inlet and simultaneously turned both inlets on.
• Finally, when the tank was full, he closed both inlets.

From the time he made the first inlet flow, how many hours did it take him to fill the tank?