Explanation:
The attached figure shows data for the cart speed, distance and time.
For low fan speed,
Distance, d = 500 cm
Time, t = 7.4 s
Average velocity,

Acceleration,

For medium fan speed,
Distance, d = 500 cm
Time, t = 6.4 s
Average velocity,

Acceleration,

For high fan speed,
Distance, d = 500 cm
Time, t = 5.6 s
Average velocity,

Acceleration,

Hence, this is the required solution.
Both organisms attempt to use the same limited sources
Wee can use here kinematics
as we know that

for shorter tree we know that


now since we know that other tree is twice high
So height of other tree is y = 39.2 m
now again by above equation



so the time taken is 2.83 s
Answer:
I think that the answer might be d