The concentration of bleach solutions sold in stores has changed throughout the country. The new, stronger bleach solution available in many stores is now 8.25% sodium hypochlorite solution. The former concentrated bleach is no longer available at many stores. The new 8.25% solution is being produced by both brand name companies as well as companies that produce generic products. The new 8.25% bleach concentration is thirty percent more concentrated than the former bleach. What was the approximate % by mass concentration of the old bleach?

A) 4.93%

B) 5.85%

C) 6.35%

D) 5.28%