[R] is it possible to map 2 plots(c and d) in a single output plot?

[newbie_2010]

is it possible to map 2 plots(c and d) in a single output plot?

library(ggplot2)
c <- ggplot(mtcars, aes(qsec, wt))
d <- ggplot (mtcars, aes(qsec, wt))
c + stat_smooth(fill="darkgrey", colour="blue", size=2, alpha = 0.2)
d + stat_smooth(fill="darkgrey", colour="red", size=2, alpha = 0.2)
-- 
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