Five stations (S1-S5) are connected to an extended LAN through transparent bridges (B1 and B2), as shown in the figure below. Initially, the forwarding tables are empty. Suppose the following stations transmit frames: S2 transmits to S1, S5 transmits to S4, S3 transmits to S5, S1 transmits to S2, and S5 transmits to S4. Fill in the forwarding tables with appropriate entries after the frames have been completely transmitted