关于这道题我想问，为啥lease rate和storage cast 会同时出现

问题如下：

A risk manager at a commodity trading company wants to reduce the firm's risk exposure by selling 1,000 kilograms of commodity ST with a 1-year forward contract. Before entering into the position, the manager wants to estimate the fair forward price of commodity ST and gathers the following information:

· Spot price of commodity ST: JPY 5,201 per kilogram

· Annualized lease rate: 2.25%

· Present value of the annual storage cost for commodity ST: JPY 65 per kilogram

· Annually compounded risk-free interest rate: −0.35%

Assuming zero convenience yield, which of the following is the best estimate of the fair 1-year forward price of commodity ST?

选项：

A.

JPY 5,005

B.

JPY 5,132

C.

JPY 5,366

D.

JPY 5,403

解释：

B is correct. The relationship between the variables is

where S is the spot price, U is the present value of the storage cost, R is the risk-free rate of interest and L is the lease rate.

First, calculate the ratio of 1 + R / 1 + L which is 0.9965/1.0225 or 0.9746

Then F = (5,201 + 65) * 0.9746 or 5,132.

A is incorrect. It uses the equation F * (1 + L)^t = (S − U) * (1 + R)^t

C is incorrect. It uses the equation F = (S + U) * (1 + R + L)^t.

D is incorrect. It uses the equation F(1 + R)^t = (S + U) * (1 + L)^t.