In a balanced 3-phase electrical system, what is the phase displacement angle between any two adjacent phases?

In an AC parallel circuit consisting of multiple branches, the total admittance (Y) is the phasor sum of the individual branch admittances. Which of the following expressions correctly represents the magnitude of the total admittance in terms of total conductance (G) and net susceptance (B)?

What happens to the phase angle between the voltage and the current in a series resistor-inductor (R-L) circuit when the frequency of the applied AC voltage is increased?