Bronn took out a fully amortizing, $5/1$ hybrid, adjustable rate mortgage of $ $139488\mathrm{.}33$ with $18-$year maturity.

The interest rate is indexed to SOFR and the margin is $3\%.$

At the time of the loan origination, SOFR was $1\%.$ The lender, however, offers a teaser rate of $2\%$ during the first $5$ years.

Note that the accrual rate is still based on the SOFR and the $3\%$ margin.

Bronn$$s monthly payment during the $4$th year equals $ $\_\_\_\_\_\_$ per month.