adding a curve with xaxs="i"

I want the curve to touch the y axis like the curve touches the upper boundary.

How can I eliminate the margin between axis and curve on the left side?

x1 <- c(1,2,3,4,5)
x2 <- c(2,4,6,8,10)
mod <- lm (x2~x1)
hm <- function (x) (mod$coe[1]+x*mod$coe[2])
plot.new()
# ...
box()
curve (hm,lty=1,add=T,xaxs="i",yaxs="i")

(R 2.8.1)

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