Each unit has 12 pages
On 9 pages you have to write something
You can cover the whole unit, except for the paragraph and essay, in 30 minutes.
The whole unit and the Paragraph takes about 1 hour. If you also do the Essay, 2 hours.
So. Choose your grade:
C = Do the first 8 pages. Takes 30 minutes.
B = Do the first 8 pages and the Descriptive Paragraph. 1 hour.
A = Do the first 8 pages, Descriptive Paragraph and the TOEFL Essay. 2 hours.