b)between 0.563 and 0.737
c)between 0.476 and 0.824
d)between 0.389 and 0.911
The simple answer is D :)
The new mean becomes 87 (40*2+7), while the new standard deviation becomes 10 (5*2). The correct option is then option D.
hope this helps! please give brainliest :)