Manual procedure with formulas and no excel

A young couple has made monthly payments (of equal size, rounded to the nearest cent) over the past 10 years on a 25 -year mortgage with Banco Popular. The stated annual rate on the mortgage is 7.25%, compounded semi-annually. They are going to renegotiate their mortgage so that they can pay off their loan over the next 5 years at a lower rate of 5% compounded semi-annually. The first payment at the new rate will be made at the end of the month immediately following the renegotiation. After careful planning they calculate that they will need to spend $1,200 of their monthly income on their mortgage payments to completely pay off the mortgage in 5 years. Assuming that this is affordable to them, and, as a result of the change to the lower rate and the shorter term, by how much have they increased their payment? A young couple has made monthly payments (of equal size, rounded to the nearest cent) over the past 10 years on a 25 -year mortgage with Banco Popular. The stated annual rate on the mortgage is 7.25%, compounded semi-annually. They are going to renegotiate their mortgage so that they can pay off their loan over the next 5 years at a lower rate of 5% compounded semi-annually. The first payment at the new rate will be made at the end of the month immediately following the renegotiation. After careful planning they calculate that they will need to spend $1,200 of their monthly income on their mortgage payments to completely pay off the mortgage in 5 years. Assuming that this is affordable to them, and, as a result of the change to the lower rate and the shorter term, by how much have they increased their payment