Read the following passage and solve the questions based on it.
For a motorist, there are three ways of going from city A to city C by a 20 km long, toll highway the toll for which is
Rs 25 per entry; a 10 km long tunnel between the two cities, the toll for which is Rs 40 per entry; and a two-lane, toll-free highway which goes 30 km east to city B and then 20 km north-west to city C.
The running cost of the motorist Re 1/km.
According to a new system, motorists are supposed to pay a bribe at the starting of their journey. This bribe has to be a one-time bribe only and no other bribe is to be paid during the earlier journey. What should be the bribe amount at the toll highway such that the total expenses on the toll highway become equal to the total expenses on the toll-free highway?