A cylindrical water tank has an external radius of 4 m and a height of 6 m. Its outside is to be painted excluding the top base. If the cost of painting is Rs 75 per m2, find the total cost of painting the tank. (Take π=722.)
a) Rs\ 18\,857
b) Rs\ 15\,086
c) Rs\ 11\,314
d) Rs\ 15\,072