As a water engineer, you have to design a rectangular settling tank for a city in which the water demand is 10,000m3/d. After doing the column analysis, it was confirmed that a depth of 3m, an overflow rate of 20m/d of will produce satisfactory removal of solids. Assume 02 tanks are required with length to width ratio as 3 . Determine the (a) Size of the required settling tank (b) Retention time (c) Horizontal velocity