Please help i can't figure it out​

Lin is shopping for a couch with her dad and heard him ask the salesperson “how much is your commission? ” the salesperson says that her commission is 5 1/2% of the selling price. a.how much commission will the salesperson earn by selling a couch for $495? b.how much money will the store get from the sale of the couch?

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?

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