A $1m^3$ rocket$-$propellant chamber is filled with combustion gases at $3000$ K

and $7$ MPa at the instant combustion ceases. The throat area of the nozzle is

$0\mathrm{.}1m^2.$ Estimate the time it takes for the chamber pressure to drop to

$0\mathrm{.}7$ MPa $.$ Assume that at the instant combustion ceases, the chamber propel$-$

lant supply stops completely, and also that $=1\mathrm{.}2$ and $\frac{?}{\text{b}\text{a}\text{r}}(M)=20.$