Finding the periodic payment of a mortgage

This video shows an application problem involving the computation of the periodic payments and the cost of financing a mortgage. The problem solved is the following:
Daniel purchased a condominium apartment for $690,000 with 25% down and monthly payments amortized over twenty-five years. If interest is 4.5% compounded semi-annually,
a) what is the size of the monthly payments?
b) What is the cost of financing?