During S-phase in a human cell, the entire genome (approximately 6x109 bp) is copied. The enzymes that copy the DNA are not perfect. As they polymerise the new strands they add the wrong nucleotide approximately 200,000 times. Most of these are fixed, but the fixing is not perfect either. A mistake that is not fixed becomes a mutation. Which of the following is closest to the number of mutations that arise during replication of the human genome?