HELP! I will report you if you give a bs answer :)

19. A certain chain saw requires a fuel mixture of 5.5% oil and the remainder gasoline. How many liters of 2.5% mixture and how many of 9% mixture must be combined to produce 40.0 liters of 5.5% mixture?

A. 12 4/23 liters of 2.5% and 28 19/23 liters of 9%
B. 28 19/23 liters of 2.5% and 12 4/23 liters of 9%
C. 21 liters of 2.5% and 18 liters of 9%
D. 18 6/13 liters of 2.5% and 21 7/13 liters of 9%
E. 21 7/13 liters of 2.5% and 18 6/13 liters of 9%
F. 18 7/13 liters of 2.5% and 21 6/13 liters of 9%

20. Mary can row at the rate of 4 miles per hour in still water. Rowing downstream in a river, she can travel 3 times as far in 1 hour as she can rowing upstream. What is the rate of flow in the river?

A. 1 miles per hour
B. 2.5 miles per hour
C. 4 miles per hour
D. 2 miles per hour
E. 3.5 miles per hour
F. 3 miles per hour