David purchased a property for $$2$ million and arranged a mortgage with DBS Bank to borrow $80\%$ of the property value. The current mortgage rate is $3\mathrm{.}5\%$ p$.$a$.$ David intended to repay his mortgage over $20$ years. The mortgage repayment is made at the beginning of every month. Required:

$($a$)$ Compute the principal and interest repayments separately, which David has paid in total for first

$3$ months.