The M & T Property Development's acquisition of a plot of land priced at R$1600000.$ The company initiated the purchase with a $30\%$ cash down payment and opted to finance the remaining balance. The loan terms mandate monthly payments over a $20-$year period, with a compound monthly interest rate of $9,20\%$ per year. What is the monthly mortgage payment?

$1.$

R $9036,25$

$2.$

R $10221,44$

$3.$

R $25301,16$

$4.$

R$124445,56$