**Official Guide**

In Country C, the number of transactions made by various noncash methods in 2006 and 2009 are shown in the graphic. All other transactions were made with cash. (see the graph below).

If the total value of all credit card transactions in 2009 was 10% more than the total value of all credit card transactions in 2006, then the average (arithmetic mean) value of credit card transactions increased by ___________ % from 2006 to 2009.

A. 2.0

B. 17.4

C. 21.0

D. 22.0