bathtub.s<-function(){
	p1 <-c(0.09, 6, 1)
	t<- seq(0,30, by=0.5)
	h1 <- p1[1]*t+p1[2]/(1+p1[3]*t) 
	motif()
	plot(t, h1, xlab="Time", ylab="Hazard function",type="l",lty=1,lwd=1,
		xlim=c(0,32), ylim=c(0,7))
	title("'bathtub' hazard function with alpha=0.09, beta=6, gamma = 1")
}