$17\mathrm{.}10$ Given the conditions of Problem $17\mathrm{.}9,$ except that the outside temperature of the masonry brick cannot exceed $325K.$ by how much must the thickness of kaolin be adjusted to satisfy this requirement?

$T_0=325k,q^{\text{'}}$ conv $=h(T-T_{})$

$q_{\text{c}\text{o}\text{n}\text{v}}^{\text{'}\text{'}}=23(325-300)$