Calculations with steam mixed with additional steam at a different pressure.

A steam press at 650Kpa + dryness fraction of 0.9% flows along a pipe at a rate of 3.5Kg per second. Steam mixes with additional steam that has been throttled from a pressure of 2000Kpa to a pressure of 800Kpa which enters from a branch pipe. If the resulting mixture is dry at 800Kpa find the amount of additional steam entering from the branch pipe?