The mass defect of the nuclear reaction ${}_5\mathrm{B}^8{\to }_4{\mathrm{Be}}^8{+}_1{\mathrm{e}}^0$ is $\mathrm{\Delta m}$. The wrong expression is/are

A sample containing $1.68\times {10}^{11}$ atoms of  ${}_{38}{}^{90}\mathrm{Sr}$ originally has an activity of $0.500 \mathrm{m} \mathrm{Ci}$ .

What is the specific activity of the sample?

What will the activity of the sample be after $30$ years?

For two different disintegration half-lives are equal at equilibrium. This is possible when