Answer:
the client should wait 10 more years until the contract is worth $180,000 since he will earn a slightly higher interest rate
Explanation:
we must determine the effective interest earned by the client if he accepts the company's proposal:
future value = present value x (1 + r)ⁿ
121,000 = 100,000 x (1 + r)⁵
(1 + r)⁵ = 121,000 / 100,000 = 1.21
⁵√(1 + r)⁵ = ⁵√1.21
1 + r = 1.0389
r = 0.0389 = 3.89%
if the client waits 10 more years until he is able to annuitize the account, he should earn:
180,000 = 100,000 x (1 + r)¹⁵
(1 + r)¹⁵ = 180,000 / 100,000 = 1.80
¹⁵√(1 + r)¹⁵ = ¹⁵√1.80
1 + r = 1.03996
r = 0.03996 = 4%