In a quarterly model with a zero inflation steady state,
- a four percent interest rate implies \beta\approx 0.99
- a ten percent markup implies \varepsilon=11 as the gross steady markup is \frac{\epsilon}{\epsilon-1}
- five months average price duration is 1.6667 quarters. With \theta=0.4, the average price duration 1/(1-\theta)=1.6667
- You need to make the slope of the PC equal, i.e. \frac{\varepsilon-1}{\gamma}=\frac{(1-\theta)(1-\beta\theta)}{\theta} and therefore \gamma =\frac{(\epsilon-1)\theta}{(1-\theta)(1-\beta\theta)} which should be 11.0375
See