53. Swimming Pool Levels The graph of Water in a Swimming Pool
\( y = f ( x ) \) represents the amount of water in thousands of gallons remaining in a swim- ming pool after \( x \) days. (a) Estimate the initial and final amounts of water contained in the pool. (b) When did the amount of water in the pool remain constant? (c) Approximate \( f ( 2 ) \) and \( f ( 4 ) \) . (d) At what rate was water being drained from the pool when \( 1 \leq x \leq 3 \) ?