GCSE Maths question - what's the correct answer

[Suffolkelfie]

My daughter is year 9. She is doing some maths using an old GCSE textbook that we have at home.
The question in the photo has an answer of 15 according to the book. She worked it out as 4.28. She has done other similar questions and got them right. Can anyone explain how to get 15 please.

So the full circumference is 12Pi.
Diameter is 12. Radius is therefore 6

Area = 36pi

Minor arc is 5/12 of the circle

5/12 of 36 is 15

Something like that

Many thanks for the quick response. It gets quite frustrating if you can't get the correct answer.