I tried working it out but I am not sure
1 plane burns 60x3.9x10^3
= 234x10^3 mls per minute
Required amount =
234x10^3 x 5.1x10^3
= 11934x10^6
= 1.1934x10^10 MLS Answer
To find the slope of the line, use the rise over run formula:

Take any two points from the line and plug them into the formula.
(0,0) and (10, 5)

The slope of the line is 0.5.
Using the form y = mx, the following equation will be your answer:
Hope this helps, even though I do feel that it could be wrong. Welp, I gave it my best shot.