I don't think I did the question right. Please check my solution and correct it! Is there a simple way of calculating this (it's very tedious...)?

First 24 months (monthly):Consider a $100,000 loan with the following 48-month repayment schedule. You are to repay an equal amount every month for the first 24 months, and every two months afterwards. There are 36 equal installments in total. The first repayment date is one month from now. The effective monthly interest rate is 0.50%. How much is each of the installments?

PV = X(1/1.005)^1 + X(1/1.005)^2 + X(1/1.005)^3 +...+X(1/1.005)^24

= X(1/1.005^1 + ... + 1/1.005^24) = 22.5628662X

Last 24 months (bi-monthly):

PV = X(1/1.005)^2 + X(1/1.005)^4 + X(1/1.005)^6 + ... + X(1/1.005)^12

PV = X(1/1.005^2 + 1/1.005^4 + 1/1.005^6 + ... + 1/1.006^12

= 5.79497859X

(5.79497859X)/ (1.005^12) = 5.45832128X

(monthly and bi-monthly total):

PV = 5.45832128X + 22.5628662X = 28.0211875X

(Installments):

100,000 = 28.0211875X

X = 3568.73