A person has manufactured a water tank in the shape of a closed right circular cylinder . The volume of the cylinder is `(539)/(2)` cubic units . If the height and radius of the cylinder be h and r , then :
Let the total surface area of the closed cylinderical tank be S, given be `S = (539)/(r) + 2pir^(2)`
If the total surface area of the tank is minimum , then the value of r will be :

Options

A. r = 7 cm
B. r = 14 cm
C. r = 49 cm
D. `r = (7)/(2)` cm