Answer:
K = 151.9422481
Step-by-step explanation:
At the end of year 10, your perpetuity is worth 100/i
(1) is worth 90×s_{10%i}
So if you set them equal you get 90*[(1+i)^10 - 1]/i = 100/i or [(1+i)^10 - 1] = 10/9 or (1+i)^10 = 19/9 or i = 0.077583937
So now the question compare (1) to (2), at t = 0
(1) is worth 90×a_{10%i} = 90(1 - 1/(1.077583937)^10)/0.077583937 = 610.5441743
(2) is worth K×a_{5%i} = 4.018264714×K
Therefore K = 151.9422481