A cellular telephone operates in the $860-$ to $900-$MHz band and has a power output of $0\mathrm{.}600$ W from an antenna $10\mathrm{.}0$ cm long. $($a$)$ Find the average magnitude of the Poynting vector $4\mathrm{.}00$ cm from the antenna, at the location of a typical person$$s head. Assume that the antenna emits energy with spherical wave fronts. $($The actual radiation from antennas follows a more complicated pattern.$)($b$)$ The ANSI$/$IEEE C$95\mathrm{.}1-1991$ maximum exposure standard is $0\mathrm{.}57$ mW$/$cm$2$ for persons living near cellular telephone base stations, who would be continuously exposed to the radiation. Compare the answer to part $($a$)$ with this standard.