Hey I’m sorry but I do not know the answer.
Notice this is a geometric progression since each number multiplied by some factor equals the next number in the sequence, in this case,

Then by applying the formula for sum to infinity of a geometric progression,
823.582% increase between the initial price and the current price.
Answer:
√308 or 17.5
Step-by-step explanation:
c^2=a^2+b^2
c^2-a^2=b^2
Substitute
18^2-4^2=b^2
324-16=b^2
b^2=308
b=√308 or b=17.5
If i remember correctly.. it’s C, you cant have the X values repeating.