This is a question on nonparametric estimation of survival function.thank you

1. Based on remission duration data (in weeks) for 21 children with acute leukemia, the Kaplan Meier estimate of S(10) is S(10) =0.7529 with estimated standard error 0.09635. Use delta method to obtain an estimated standard error for @{S(10)}, where (.) is the inverse (note: not reciprocal) function of the standard normal cumulative distribution function P(z) = p(x)dx , and $(x) = is the standard normal probability density function. Obtain an approximate 95% confidence interval for @-{S(10)}, and transform it back to yield a confidence interval for S(10) of the form (@(a), D(b)). Note: You need to know how to differentiate an inverse function. You can use the R function gnorm to compute {S(10)}, and pnorm to evaluate (@(a), D(b))