$($a$)$ A $10$ mm diameter Brinell hardness indenter produced an

indentation $2\mathrm{.}5$ mm in diameter in a steel alloy when a load of

$1000$ kg was used. Compute the HB of this material. $($b$)$ What

will be the diameter of an indentation if $500$kg load is used on a

material with Brinell Hardness number $300$ HB$?$