The figure shows a purely convergent nozzle with a steady, inviscid compressible flow of an ideal gas with constant thermophysical properties operating under choked condition. The exit plane shown in the figure is located within the nozzle. If the inlet pressure $\left(P_{0}\right)$ is increased while keeping the back pressure $\left(P_{back}\right)$ unchanged, which of the following statements is/are true?

1. Mass flow rate through the nozzle will remain unchanged.
2. Mach number at the exit plane of the nozzle will remain unchanged at unity.
3. Mass flow rate through the nozzle will increase.
4. Mach number at the exit plane of the nozzle will become more than unity.