$A$ shopkeeper gives two successive discounts of $7 \%$ each on the marked price of $Rs.\, 20,000$ of an article. The selling price of the article is (in $Rs.$):

What was the rate of discount if a computer with a marked price of $Rs. 30,000$ was sold for $Rs. 28,000$? (in $\%$)

$A$ sells a car priced at $Rs. 36,000$. He gives a discount of $8\%$ on the first $Rs. 20,000$ and $5\%$ on the remaining $Rs. 16,000$. $B$ also sells a car of the same make,priced at $Rs. 36,000$. He gives a discount of $7\%$ on the total price. Calculate the actual prices charged by $A$ and $B$ for the cars (in $Rs.$).

The true discount on a certain bill due for nine months at $4 \%$ simple interest is $Rs.\, 150$. Find the amount of the bill (in $Rs.$).

$Rs. 20$ is the true discount on $Rs. 260$ due after a certain time. What will be the true discount on the same amount due after half of the earlier time,the rate of interest being the same? (in $Rs.$)

If the simple interest on a certain sum for some years at $6 \%$ is $Rs. 180$,and the true discount at $5 \%$ on the same amount for the same time is $Rs. 140$,find the sum (in $Rs.$) and the time (in $years$).