b. In the current spreadsheet, u = 30, f = $20, and $800 is the flat commission for sales equal to or smaller than u. This means that your salesperson will collect a flat $800 for selling u = 30 pairs of jeans. Once she sells 31 pairs or more, she will collect f = $20 for each additional pair sold. Which two linear equations describe the two intervals of N(x)? Express your answer in terms of u, f, and x, where x is the number of units sold. You may study the formulas in the spreadsheet if you find them helpful. Type your response here: Interval Equation first {x s u} N(x) = 30x+20 second {u = x} N(x) = 20x+20+800