A thermodynamic system is taken from an original state A to an intermediate state B by a linear process as shown in the figure. Its volume is then reduced to the original value from B to C by an isobaric process. The total work done by the gas from A to B and B to C would be:

Step 1: Identify the initial and final states and the type of processes. The system starts at state A, goes to state B via a linear process, and then from state B to state C via an isobaric process. From the graph: State A: $P_A = 8000 \, Dyne/cm^2$, $V_A = 3 \, m^3$ State B: $P_B = 4000 \, Dyne/cm^2$, $V_B = 7 \, m^3$ State C: The process B to C is isobaric, so $P_C = P_B = 4000 \, Dyne/cm^2$. The volume at C is reduced to the original value from A, so $V_C = V_A = 3 \, m^3$.

Step 2: Convert pressure units to SI units (Pascals). We know that $1 \, Dyne/cm^2 = 0.1 \, N/m^2 = 0.1 \, \text{Pa}$. $P_A = 8000 \, Dyne/cm^2 = 8000 \times 0.1 \, Pa = 800 \, \text{Pa}$ $P_B = 4000 \, Dyne/cm^2 = 4000 \times 0.1 \, Pa = 400 \, \text{Pa}$ $P_C = 400 \, \text{Pa}$

Step 3: Calculate the work done during the process A to B ($W_{AB}$). The process A to B is a linear process on a P-V diagram. The work done is the area of the trapezoid under the line segment AB. $W_{AB} = \frac{1}{2} (P_A + P_B) (V_B - V_A)$ Substitute the values: $W_{AB} = \frac{1}{2} (800 \, Pa + 400 \, Pa) (7 \, m^3 - 3 \, m^3)$ $W_{AB} = \frac{1}{2} (1200 \, Pa) (4 \, m^3)$ $W_{AB} = 600 \, Pa \times 4 \, m^3$ $W_{AB} = 2400 \, \text{J}$

Step 4: Calculate the work done during the process B to C ($W_{BC}$). The process B to C is an isobaric process (constant pressure). The work done is given by $W = P \Delta V$. $W_{BC} = P_B (V_C - V_B)$ Substitute the values: $W_{BC} = 400 \, Pa (3 \, m^3 - 7 \, m^3)$ $W_{BC} = 400 \, Pa (-4 \, m^3)$ $W_{BC} = -1600 \, \text{J}$

Step 5: Calculate the total work done ($W_{total}$). The total work done is the sum of the work done in each process. $W_{total} = W_{AB} + W_{BC}$ $W_{total} = 2400 \, J + (-1600 \, J)$ $W_{total} = 800 \, \text{J}$

The final answer is $\boxed{800 J}$.