What is the difference in the monthly repayments between two alternative on a house valued at $$510,000?$ Option A is a $90\%$ LTV loan over $30$ years at $6\mathrm{.}45\%.$ Option B is a $95\%$ LTV loan over $20$ years at $7\mathrm{.}25\%.$ Calculate the difference as Option A minus Option B$.$a$)$ $$301\mathrm{.}48$b$)-$$$943\mathrm{.}26$c$)-$$$613\mathrm{.}65$d$)-$$$1,068\mathrm{.}491$