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For the signal flow graph shown in the figure, the value of $\dfrac{C(s)}{R(s)}$ is

1. $\dfrac{G_{1}G_{2}G_{3}G_{4}}{1 – G_{1}G_{2}H_{1} – G_{3}G_{4}H_{2} – G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}} \\$
2. $\dfrac{G_{1}G_{2}G_{3}G_{4}}{1 + G_{1}G_{2}H_{1} + G_{3}G_{4}H_{2} + G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}} \\$
3. $\dfrac{1}{1 + G_{1}G_{2}H_{1} + G_{3}G_{4}H_{2} + G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}} \\$
4. $\dfrac{1}{1 – G_{1}G_{2}H_{1} – G_{3}G_{4}H_{2} – G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}}$