In the first stage of a letter-writing campaign, a person writes the same letter to each of 3 pen pals. In the second stage, each of these 3 pen pals copies the letter and sends it to 3 other pen pals, and so on, following this pattern. If it is assumed that no pen pal receives a letter twice, the least number of stages it would take until the minimum total sum of pen pals who received the letter is 9 800 is

Select one:

a.

7

b.

10

c.

9

d.

8