Aviator Station, Inc. operates a chain of high$-$end athletic apparel stores. The stores sell ten different styles of sweatpants with identical unit costs and selling prices. A unit is defined as one pair of sweatpants. Each store has a manager who is paid a fixed salary. Individual salespeople receive a fixed salary and a sales commission. Aviator is trying to determine the desirability of opening another store, which is expected to have the following revenue and cost relationships: Refer to the original data. Calculate the number of units sold where the operating profit under $($a$)$ a fixed salary plan discussed in $(4)$ above and $($b$)$ a lower fixed salary and commission plan $($for salespeople only$)$ would be equal. Above that number of units sold, one plan would be more profitable than the other; below that number of units sold, the reverse would occur.