It costs Rs. p each to send the first thousand messsages and Rs. q to send each subsequent one . If r is greater than 1,000, how many Rupees will it cost to send r messages ?

A 1000 (r - p) + pq

B 1000 p + qr

C 1000 (r - q) + pr

D 1000(p - q) + qr

Correct Answer: Option D

We need to find the total cost to send r messsages, r > 1000.

The first 1000 messsages will cost Rs.p each (Or)

The total cost of first 1000 messsages = Rs.1000p

The remaining (r - 1000) messsages will cost Rs.q each (Or)

The cost of the (r - 1000) = Rs.(r - 1000)y

Therefore, total cost = 1000p + rq - 1000q

= 1000(p - q) + qr