Nana has a water purifier that filters \dfrac13 3 1 start fraction, 1, divided by, 3, end of the contaminants each hour. she used it to purify water that had \dfrac12 2 1 start fraction, 1, divided by, 2, end fraction kilogram of contaminants. write a function that gives the remaining amount of contaminants in kilograms, c(t)c(t)c, left parenthesis, t, right parenthesis, ttt hours after nana started purifying the water.