Final answer:
The calculation involves using present value of an annuity due formula to find the present value of monthly lease payments over 6 years at an annual compounded interest rate, requiring conversion to monthly rates for accuracy.
Step-by-step explanation:
The subject of this question falls under Mathematics, specifically in the area of financial mathematics which deals with the calculation of present value of a series of payments or cash flows. The grade level would be College, given the complexity of the financial concepts involved. To calculate the present value of a lease contract with payments of $900 at the beginning of every month for 6 years at a lease rate of 4.5% compounded annually, we would use the present value of an annuity due formula. However, since the compounding frequency of the interest rate is annual and the payments are monthly, we should convert the annual interest rate to a monthly rate and the number of years to the number of months for accurate calculation. This process involves fairly advanced financial mathematics and is typically taught at the collegiate level in finance-related courses.