194. According to the figure below, inside a U-shaped tube connected to a gas reservoir, the space is equally filled with water and oil. What is the gas pressure in the reservoir in millimeters of mercury?
[Figure: A U-shaped tube with a gas reservoir on the left side; water at the bottom and oil on the right; the height difference is labeled $68\,\text{cm}$.]$$\left(\rho_{\text{mercury}} = 13/6\,\frac{\text{g}}{\text{cm}^3},\quad \rho_{\text{water}} = 0/8\,\frac{\text{g}}{\text{cm}^3},\quad \rho_{\text{oil}} = 0/8\,\rho_{\text{water}},\quad g = 10\,\frac{\text{m}}{\text{s}^2}\right)$$
- [(1)] $1$
- [(2)] $5$
- [(3)] $10$
- [(4)] zero