A sensor is reading over time, where $t\ge 0$ is given by: $R\left(t\right)=50-0.1t$, which is written using arbitrary units. A calibration function is: $C\left(x\right)=2x+10$, and a safety check computes: $S\left(y\right)=\sqrt{y-40}$. Determine the set of times $t$ for which the composed safety reading: $(S\circ C\circ R)\left(t\right)$ is defined. Express your answer as an interval(s) of $t$.