In practice, price is the most often-changed variable. Businesses can quickly react to competitors or low sales through coupons, sales events, or other price-reduction methods. Once you have a product to sell, you must be able to identify who to sell it to. Target marketing and market segmentation are techniques used for this purpose. Demographics and geography are common methods of segmenting the market.
Different consumers buy different products at different times.
What might be a seasonal product in one area of the country or world might be a year-round item in another. And the same product would need to be marketed differently in different areas. Certain products may appeal to specific age groups or economic classes. Marketing luxury cars to college students who can't afford them would be a waste of effort. Along the same lines, marketing economy cars to single, professional, affluent consumers might not achieve a very good return.