The book area per side is given. The area taken by the book (taking both sides and the thickness will be
side 1+thickness+side2 + folded lengths 1 + folded length 2.
Or 10 cmx18cm+2cmx18cm +(10cm x 18cm) +(5cmX18cm)+(5cm x18cm)
= 18( (10+2+10+5+5)
=18cm x32 cm will be required for the jacket
Area of the jacket paper = 576 square cm.
Here we have assumed that the book is 18 cm in length and 12 cm in breadth(this means the margin paper has to be taken extra which has been done)