When Juan had $4$ years left in college, he took out a student loan for $$15,630.$ The loan has an annual interest rate of $3\mathrm{.}9\%.$ Juan graduated $4$ years after acquiring the loan and began repaying the loan immediately upon graduation.

According to the terms of the loan, Juan will make monthly payments for $5$ years after graduation. During the $4$ years he was in school and not making payments, the loan accrued simple interest.

Answer each part. Do not round intermediate computations, and round your answers to the nearest cent. If necessary, refer to the list of financial formulas

$($a$)$ If Juan's loan is subsidized, find his monthly payment.

Subsidized loan monthly payment: $

$($b$)$ If Juan's loan is unsubsidized, find his monthly payment.

Unsubsidized loan monthly payment: