B has a typo. See Long Version of Correction for a table and detailed explanation. 5-11, page 37. This question is starred, but the answer is actually in the back of the book, not on the Web site. Answer to 2-3, Part B was accidentally omitted.
Answer is zero.
The definition of an exon given in the glossary of the Purves text is incorrect. There are errors in the structures of mannose and fructose in the Purves text Fig. In fructose, there should be an OH above the ring on carbon 2 and an OH above the ring on carbon 3. 15-11 in Becker implies that simultaneous removal of primer and its replacement occurs without adding on to the 3' end of the next fragment. This is an error.