3. (Silver contract) At the beginning of April one year, the silver forward prices (in cents per troy ounce) were as follows: Apr 406.50 July 416.64 Sept 423.48 Dec 433.84 (Assume that contracts settle at the end of the given month.) The carrying cost of silver is about 20 cents per ounce per year, paid at the beginning of each month Estimate the interest rate at that time. y