$($a$)200$ C$100$ C $,0\mathrm{.}05m.(r_0)0\mathrm{.}05m0\mathrm{.}1m..$

$\frac{1}{r}\frac{d}{dr}(r\frac{dT}{dr})=0$

$(15).1-6,$

$r=r_0+r(i-1)=0\mathrm{.}05+0\mathrm{.}01(i-1)$

Thomas $(35).$

$x_n={}_n$

$x_i={}_i-\frac{e_i{x}_{i+1}}{{}_i},i=n-1,n-2,$dots,$1$

${}_1=d_1$

${}_1=\frac{b_1}{{}_1}$

${}_i=d_i-\frac{c_i{e}_{i-1}}{{}_{i-1}},i=2,3,$dots,$n$

${}_i=\frac{b_i{c}_i{}_{i-1}}{{}_i},i=2,3,$dots,$n$