(Answered) : The value of critical ratio is closer to 55% (demand = 15), but why the solution of this question chose rounded up to 80%(demand =

The value of critical ratio is closer to 55% (demand = 15), but why the solution of this question chose rounded up to 80%(demand = 20)? I am wondering when to round up for the optimal quantity.

The value of critical ratio is closer to 55% (demand = 15), but why the solution of this question chose rounded up to 80%(demand = 20)? I am wondering when to round up for the optimal quantity.

https://d2vlcm61l7u1fs.cloudfront.net/media%2F065%2F06504899-cd94-4b1d-beb1-270c21dd7581%2FphpzfEsBL.png

Cumulative Probability 10% 30% 55% 80% 95% 100% Demand Probability 10 15 20 25 30 10% 20% 25% 25% 15% 5% Cu-S11.24, Co-$5.76 Critical ratio = 11.24 =0.661176