Let z=sqrt(49-x2-y2) .... find the volume removed by the drill bounded by the x-y, x-z and y-z planes and muliply by 8, then subtract that from 49*4/3pi for the final answer.
The volume removed by the drill = 8* (double integral of zdxdy ) the x limits are 0 to sqrt(25-y2) and the y limits are 0 to 5. I got 952pi/3.