The formula of getting the surface area of the sphere is = 4πr2
For surface area of a hemisphere use 2πr2
To get an area of hollowed hemisphere, you need to add outer surface area, inner surface area and area of ring.
Now you get:
2π(1.25)2 + 2π(1.86/2)2 + ( π(1.25)2 - π(1.86/2)2 )
3π(1.25)2 + π(1.86/2)2
3π(1.25)2 + π(0.93)2
14.71875 + 2.715786
17.43454
17.43 cm2
Hope this will help!