McKenzie Wood Products negotiated a $$200,000$ revolving line of credit with the Bank of Montreal at prime plus $2\%.$ On the $20$th of each month, interest is calculated $($up to but not including the $20$th$)$ and deducted from the company's chequing account. If the initial loan advance of $$25,000$ on July $3$ was followed by a further advance of $$30,000$ on July $29,$ how much interest was charged on July $20$ and August $20?$ The prime rate was at $3\%$ on July $3$ and fell to $2\mathrm{.}75\%$ on August $5.$