Department Store Sales The graph in Fig. 1 shows the total sales in thousands of dollars i...

Department Store Sales The graph in Fig. 1 shows the total sales in thousands of dollars in a department store during a typical 24-hour period.

Figure 2

(a) Estimate the rate of sales during the period between 8 a.m. and 10 a.m.

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(b) Which 2-hour interval in the day sees the highest rate of sales and what is this rate?