Periodic energy usage. The 168-vector w gives the hourly electricity consumption of a manufacturing plant, starting on Sunday midnight to 1AM, over one week, in MWh (megawatt-hours). The consumption pattern is the same each day, i. e., it is 24-periodic, which means that wt+24 = wt for t = 1,...,144. Let d be the 24-vector that gives the energy consumption over one day, starting at midnight. (a) Use vector notation to express w in terms of d.