Determine the time needs to fill completely the tank when all pipes are open together? if you know that: $1.$ If ONLY Pipe S$1$ is open, it needs $10$ seconds to fill this tank by its self. $2.$ If ONLY Pipe S$2$ is open, it needs $20$ seconds to fill this tank by its self. $3.$ If ONLY Pipe S$3$ is open, it needs $30$ seconds to fill this tank by its self. $4.$ If ONLY Pipe S$4$ is open, it needs $40$ seconds to fill this tank by its self.