[R] regex - extracting 2 numbers and " from strings

[Omar André Gonzáles Díaz]

Hi I have a vector of 100 elementos like this ones:

a <- c("SMART TV LCD FHD 70\" LC70LE660", "LED FULL HD 58'' LE58D3140")

I want to put just the (70\") and (58'') in a vector b.

This is my try, but is not working:

b <- grepl('^[0-9]{2}""$',a)

Any hint is welcome, thanks.

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