A 4 pole 3 phase, 400V, 50 Hz star connected induction motor has the following per phase parameters for its circuit model (referred to the stator side)

r₁ = 1.2 Ω, X₁ = 1.16 Ω

\(r_{2}^{'}=0.4~\text{ }\!\!\Omega\!\!\text{ },\text{ }\!\!~\!\!\text{ }X_{2}^{'}=1.16~\text{ }\!\!\Omega\!\!\text{ }\)

The slip at which maximum torque occurs is ________ (up to two decimal places)