\({[ At ]= A \times \frac{1}{ T }= L }\)
\(\therefore \quad[ A ]= T ^1 L ^1\)
\(\quad \frac{ t }{ B } \text { is in meters }\)
\(\therefore \quad \frac{1}{ T [ B ]}= L\)
\(\therefore \quad[ B ]= T ^{-1} L ^{-1}\)
$1\,M.S.D. = 100\, C.S.D. = 1\, mm $