$2.$ A constant$-$area duct, $25$ cm in length and $1\mathrm{.}3$ cm in diameter, is connected to an air reservoir through a converging nozzle, as illustrated in the sketch. For a reservoir pressure of $1$ MPa and a temperature of $600$ K $,$ determine the system flow rate for a back pressure of $101\mathrm{.}3$ kPa $.$ The Darcy friction factor is $0\mathrm{.}023.$