If V = 20 V, R1 = R2 = R3 = 10 Ω, and R4 = 20 Ω in a bridge circuit configured such that R1 and R2 form one branch and R3 and R4 form the parallel branch across the source with zero source resistance, what are the Thevenin's equivalent resistance (Rth) and Thevenin's voltage (Vth) across the open terminals of R2 and R4 respectively?

While calculating Thevenin resistance (Rth) or Norton resistance (RN), independent constant current sources in the circuit are:

While calculating Thevenin resistance (Rth), constant current sources in the circuit are:

According to the Maximum Power Transfer Theorem, maximum power is delivered from a source to a load when the load resistance (RL) is equal to the internal resistance (r) of the source. At this specific condition, what is the efficiency of the power transfer?