Given edge of wooden block (a) = 21cm
Given diameter of hemisphere = edge of cube
Radius = 21/2 = 10.5cm
Volume of remaining block = volume of box – volume of hemisphere
Surface area of box = 6a2 ........(1)
Curved surface area of hemisphere = 2πr2 ..........(2)
Area of base of hemisphere = πr2
So remaining surface area of box = (1) – (2) + (3)
Remaining surface area of box = 2992.5cm2
Volume of remaining block = 6835.5cm3