The owner of Leisure Boutique in a local mall is forecasting this month's $($October$\text{'}$s$)$ demand for one of her best$-$selling products based on the following historical data: the series displays a trend.

$\backslash$table$[[$Month$,\backslash$table$[[$Qty$],[$Sold$]]],[$April$,100],[$May$,140],[$June$,110],[$July$,150],[$August$,120],[$September$160,]]$

What is this month's forecast using the naive approach?