"Up to date" sounds like they want a lump sum payment in the ninth month rather than just increasing the remaining payment so its not really a deferred annuity you just need to calculate the present value of the missed payments in minie months plus the 9nth month payement.
i= Monthly interest rate 1 1/4 %
P(i^8 +i^7 +...1) = P((i^9-1)/(i-1))
If they do mean stretching out the missed payment over the remaining years subtract P from the above amount and find the monthly payment of paying the amount for 4 years 3 months. Adds this to P to find your new monthly rate.