An individual takes out a loan of $300,000$ euros for $10$ years at a rate of $3\%.$ This loan is contracted on October $12$th $2023,$ it is repayable in constant monthly instalments of principal and interest. The first repayment is due on November $12$th$,2023.$

a$)$ What is the amount of the constant monthly repayments? b$)$ What is the interest charge on the $50$th payment?

c$)$ What is the capital repaid in the $30$th payment?

d$)$ The loan shall include a clause for the early repayment, without penalty, of the outstanding principal. The individual wishes to use this clause after the payment on $31$ December $2025,$ how much outstanding capital does he have to repay?