"how to fold a standard business letter"

no. 10 envelope (approximately 9 1/2 x 4 1/8 inches)

use this size of envelope for standard business letters.
check the inside address on the letter with the address on the envelope to be sure they correspond.
be sure that the letter is properly signed.
place the letter faceup on the desk.
with the edges even at the sides, crease the fold.
fold the top downward so that the top edge of the letterhead is within half an inch of the bottom fold. with the edges even at the sides, crease the fold.
insert the letter into the envelope with the last crease toward the bottom of the envelope.

these steps are not complete. which step needs to be added to make this procedure clearer, and where should it be inserted?

a.“using a ruler, measure the letter and mark off thirds,” should be inserted before step 1.
b.“fold slightly less than one-third of the letter toward the top edge of the sheet,” should be inserted after step 6.
c.“using a ruler, measure the letter and mark off thirds,” should be inserted after step 5.
d.“fold slightly less than one-third of the letter toward the top edge of the sheet,” should be inserted in step 5 before the instruction to crease the fold.