What would be Macauleys Duration of the portfolio? Also show the formula to getting there.

100,000.00 20 bond a par value (A) years period (N) coupon coupon rate years semi annual 40 4% 2000 6.00% 3.00% half yearly yearly half yearly rate $76,885.23 present value Bond B par value (A) years period (N) coupon coupon years 50000 30 30 3% 1500 years yearly rate 3.50% yearly present value $45,401.99 30,000.00 years semi annual Bond C par value (A) years period (N) coupon coupon rate rate 10 3% 450 2.50% 1.25% hafl yearly yearly half yearly present value $30,700.91 43 total value of portfolio $152,988.13