Consider a manometer formed with a U-shaped tube containing liquid of density 13.6 g/cm³ and connected to a frustum by the upper ends of the tube, as shown in the figure. Air flows inside the frustum at a rate of 900 cm³/s. Air is assumed to be an ideal fluid. Determine the difference in height between the two vertical columns of the manometer.

• A. 2.1 cm
• B. 5.4 cm
• C. 7.7 cm
• D. 11 cm

Answer: (C)