$(10)A2m{g}^{27}Al$ foil is irradiated with a neutron flux of $1\mathrm{.}75{10}^{13}\frac{n}{c}{m}^2.$s$.$ What is the irradiation time required to produce $1\mathrm{.}5Ci$ of ${?}^{28}Al$ activity? ${}_c{(}^{27}Al)=0\mathrm{.}23b,$ half life of ${?}^{28}Al=2\mathrm{.}3$min.