The pressure at the interface is $P _{int} = P_0 + ρ g H $.

Applying bernoulli's equation between point at the interface of two liquids and exit of the tube . $P_{ i n t} + ρ g ( H/2 + H/4 )= P_0 + \frac{1}{2} ( 2 ρ ) v^2$. This doesn't give correct answer .

What is the mistake ? Thanks.