U.S. Sales and Refund Policy. Thanks for shopping at Apple. We appreciate the fact that you like to buy the cool stuff we build. We also want to make sure you have a rewarding experience while you’re exploring, evaluating, and purchasing our products, whether you’re at the Apple Online Store, in an Apple Retail Store, or on the phone with the Apple Contact Center.
If you buy an iPhone, iPad, Mac, or Apple Watch and pay in full, your credit will be applied to your original payment method up to the total purchase price after we receive your trade-in device and confirm that the condition matches what you described. For any remaining amount, you’ll receive an Apple Gift Card by email.
This depends on the model of Macbook Pro (i.e. the screen size - 13.3", 15.4" or 17") you purchased, but the resolution and DPI (or PPI), for the 2009 unibody models, is provided by Wikipedia (here and here).
However, given the resolution and display size, you can easily calculate the PPI. In summary:
MacBook Pro 13.3": 1440x900 (127.68 PPI)
MacBook Pro 15.4": 1440x900 (110.27 PPI)
MacBook Pro 15.4": 1680x1050 (128 PPI)
MacBook Pro 17": 1920x1200 (133.19 PPI)
In ElCapitan SystemPreferences->Displays->Display tab: select the "scaled" resolution: then you see what you can set your screen to.
pixels are"combined"
