Answer:
a
Step-by-step explanation:
(I'm going to translate y' to dy/dx as it makes it easier to read for me, you could change it back if you wanted.)



(separate the variables)


(by letting c = ln k and using log laws)

(raise everything to power e)

(applying boundary conditions)
Particular solution:
21 * 10
210 fingers
Answer: 210 fingers
Let's assume the ladder's long as x
sin 45 = 7/x
1/2^0.5 = 7/x
x = 7*1.414
x = 9.9 m
so long of the ladder is 9.9 m
9,000,000? I'm not sure. Maybe wait for another answer?