Thanks. But I've been there.

Copy and pasted these commands in R:

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if (!require("drat")) install.packages("drat")
drat::addRepo("ghrr")
install.packages("RQuantLib", type="binary")
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A popup of showing various mirror sites. Tried Germany, USA, a few others and all got this message:

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Warning: unable to access index for repository https://ghrr.github.io/drat/bin/windows/contrib/3.5:
cannot open URL 'https://ghrr.github.io/drat/bin/windows/contrib/3.5/PACKAGES'
Warning message:
package ‘RQuantLib’ is not available (as a binary package for R version 3.5.0)
>
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