A merchant's position in cash is 10000 bushel of wheat, the variance of the changes of the future price is 0.00094, the variance of the changes of the base is 0.000453, the variance of the changes of the price in cash is 0.000805 and the covariance of the changes of the forward price with the changes of the prices in cash is 0.000518. Calculate the efficiency of the hedge and choose one of the following answers

a. 0.97

b. 0.31

c. 0.69

d. 0.03