Let f (t), 0 t < 24, denote the number of pints drunk in the previous hour. For example, if between 21.00 and 22.00 you had two pints of beer, then f (t) = 2 when t [22, 23). Sketch a plausible graph of f (t). (a) Explain what 23 0 f (t)dt means. (b) What does the function F (x) = x 0 f (t)dt represent?