Which of the following explains how to obtain the graph of $y=1+2e^x$ from the graph of $y=e^x$?

(a) Vertically stretch the graph of $y=e^x$ by a factor of 2 and then shift this result up 1 unit.
(b) Vertically stretch the graph of $y=e^x$ by a factor of .5 and then shift this result up 1 unit.
(c) Vertically stretch the graph of $y=e^x$ by a factor of 2 and then shift this result to the right 1 unit.
(d) Vertically stretch the graph of $y=e^x$ by a factor of .5 and then shift this result to the left 1 unit.