A flexible pavement is known to have a structural number of $4.$ The pavement is on a soil with a resilient modulus of $5500$ lb$/$in$2.$ The pavement was designed with $85\%$ reliability, an overall standard deviation of $0\mathrm{.}35,$ and a $\backslash$Delta PSI of $2\mathrm{.}0($a TSI of $2\mathrm{.}5).$ How many $18-$kip single$-$axle loads can be carried per day before the pavement reaches its TSI, if the design life is $15$ years?