One week, a certain truck rental lot had a total of 20 trucks, all of which were on the lot Monday morning. If 50% of the trucks that were rented out during the week were returned to the lot on or before Saturday morning of that week, and if there were at least 10 trucks on the lot that Saturday morning, what is the greatest number of different trucks that could have been rented out during the week?  Choose the correct option:  A) 18  B) 20  C) 12  D) 8  E) 4

Rationale: "n - not rented trucks ; r - rented trucks n + r = 20 n + r / 2 = 10 r = 20 b"
Answer: B