Bill travels west on Interstate 80 from Summerville. Sally leaves Carlton City and travels on I-80 in the same direction as Bill. Bill's distance in miles from Metro City is given byB(t) = 120 – 60tand Sally's distance in miles from Metro City is given byS(t) = 135 – 70, where t is the number of hours since noon. Write an expression for the distance separating Bill and Sally and find their separation at 2:00 PM.