The key to exercise solutions in chapter 2.2 - Grammar for the textbook Focus 2 - Student's Book with authors Daniel Brayshaw, Sue Kay and Vaughan Jones from Pearson Education
Read about e-ink. Who was Joe Jacobs and why did he have a 'Eureka!' moment?
Joe Jacobson wanted to solve the problem of not having a new book when you finished the one you are reading (see Culture notes).