To meet a U. S. Postal Service requirement, employees' footwear must have a coefficient of static friction of 0.5 or more on a specified tile surface. A typical athletic shoe has a coefficient of 0.770. In an emergency, what is the minimum time interval in which a person starting from rest can move 3.50 m on a tile surface if she is wearing the following footwear?(a) footwear meeting the Postal Service minimum(b) a typical athletic shoe in s.