Sum of First n Terms of an AP

A man bought a scooter with $12$ monthly instalments. He paid $\text{ ₹ 6,000 }$as first instalment and thereafter for each instalment he paid $\text{ ₹250}$ less than the previous month. By instalment if he paid $\text{ ₹3150}$ extra over the original price, then find the original price of the scooter.

A farmer repays his loan of $\text{ ₹ }1,18,000$ by paying every month starting with the first instalment of $\text{ ₹ }1,000\text{. }$If he increases the instalment by $\text{ ₹ }100$ every month, find the amount paid by him in $30$ instalments. What loan does he still have to pay after the $30th$ instalment ?