A casting of size 100 mm x 100 mm x 50 mm is required. Assume volume shrinkage of casting as 2.6%. If the height of the riser is 80 mm and riser volume desired is 4 times the shrinkage in casting, what is the appropriate riser diameter in mm?
(a) 14.38 (b) 20.34
(c) 28.76 (d) 57.52