air flows through a main duct at a mass flow rate of 4kg/s the main duct enters a junction that splits into two branch ducts one with a cross section of 20cm x 30cm and one with a cross section og 40cm x 60cm if the mass flow rate in the large branch is 2.8kg/s what is the flow rate in the small branch? if the density of air is p=1.16kg/m what is the velocity in each branch