According to current regulations, the maximum permissible dose of strontium-90 in the body of an adult is 1 μCi (1 × 10-6 Ci). Using the relationship rate = kN, calculate the number of atoms of strontium-90 to which this dose corresponds. To what mass of strontium-90 does this correspond? The half-life for strontium-90 is 28.8 yr.