Compute the average (mean) from the data shown. (round to the nearest whole number)

{42 , 30 , 79 , 99 , 72 , 24 , 89 , 91 , 78 , 69}
A) 67
B) 68
C) 69
D) 70

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters