T <- function(x) 0.4*x[1] + 0.2*x[2] + 0.1*x[3] + 0.1*x[4]
nrep <- 100000
dimc <- 4
x <- rnorm(dimc*nrep,mean=100,sd=10)
x <- matrix(x,nrow=nrep)
t <- apply(x,1,T)
mean(t)
var(t)
mean((t-100)^2)