Sam has the option of purchasing a car for $30,000 or leasing it for a $375 payment made at the beginning of each month for 4 years. The interest rate is 2.7% compounded semi-annually, a down payment of $7,500 is required and the residual value is $7,000 payable at the end of the lease. 

Should Sam lease or buy? 

What is the economic advantage of the better choice?