$12\mathrm{.}30$ Figure $12\mathrm{.}49$a shows a pile. Let $L=15m,D($pile diameter$)=305mm,H_f=3m,{}_{\text{f}\text{i}\text{l}\text{l}}=17\mathrm{.}5k\frac{N}{m^3},$ and ${}_{\text{f}\text{i}\text{l}\text{l}}^{\text{'}}=25.$

Determine the total downward drag force on the pile. Assume that the fill is located above the water table and that ${}^{\text{'}}=0\mathrm{.}5{}_{\text{f}\text{i}\text{l}\text{l}}^{\text{'}}.$