If H1 is the height of the liquid surface above the orifice top, H2 is the height of the liquid surface above the orifice bottom, b is the width of the orifice and Cd is the coefficient of discharge, what would be the expression to calculate the discharge denoted by Q?

• A. \(Q = \frac{1}{2} \times 3{C_d}b\sqrt {2g} (H_2^{3/2} - H_1^{3/2})\)
• B. \(Q = \frac{1}{2} \times 3{C_d}b\sqrt {2g} (H_1^{3/2} - H_2^{3/2})\)
• C. \(Q = \frac{1}{3} \times 2{C_d}b\sqrt {2g} (H_1^{3/2} - H_2^{3/2})\)
• D. \(Q = \frac{1}{3} \times 2{C_d}b\sqrt {2g} (H_2^{3/2} - H_1^{3/2})\)