A $50 \mathrm{~Hz}, 275 ~\mathrm{kV}$ line of length $400 \mathrm{~km}$ has the following parameters:
Resistance, $R=0.035 ~\Omega / \mathrm{km} ;$
Inductance, $L=1 ~\mathrm{mH} / \mathrm{km} ;$
Capacitance, $C=0.01 ~\mu \mathrm{F} / \mathrm{km} ;$
The line is represented by the nominal $-\pi$ model. With the magnitudes of the sending end and the receiving end voltages of the line (denoted by $V_{S}$ and $V_{R}$, respectively) maintained at $275 ~\mathrm{kV}$, the phase angle difference $(\theta)$ between $V_{S}$ and $V_{R}$ required for maximum possible active power to be delivered to the receiving end, in degree is ___________(Round off to $2$ decimal places).