How can we tell from an HP WiFi card spec whether the NIC is 2.4GHz or 5GHz,
or both?

I'm trying to help my sister buy an HP laptop on the web.

My problem is that I contacted HP Support (via their chat mechanism) because USA
phone support is not open now, and technical support isn't open tomorrow.

All I want to know is HOW to tell if a WiFi card has both 2.4GHz and 5GHz.

For $300 at Costco, plus $30 for shipping, this seems to be a decent 15.6-inch
display laptop:
http://www.costco.com/HP-15z-Laptop-|-AMD-E1-|-Windows-10.product.100222779.html

The main drawback from that Costco offering is that the WiFi isn't "ac", there's
no mention of bluetooth, and the laptop doesn't come with Office 2013.

But, we can fix that at the HP web site.

If we go to the HP site to buy it, we can customize it to add what Costco doesn't
have (and get free shipping).
http://store.hp.com/us/en/pdp/Laptop...&TabName=specs

0. We start with the HP price of $350 which comes with twice as much memory as
Costco's (4GB - 8GB) plus free shipping (worth $30), so it's only $20 more
than the Costco price.
1. We add the Microsoft Office Home & Student 2013 from HP for an extra $140 (either
boxed, or already installed - I suggest they get the box for easier re-use later).
https://store.hp.com/webapp/wcs/stor...tNumber=QM4342
2. We add a WiFi "ac" card from HP for an extra $30 but is it dual band, 2.4GHz and
5GHz or not?
3. We add an extra wireless mouse and keyboard (no wires!) for $30 (because my sis
wants that).
https://store.hp.com/webapp/wcs/stor...=LV290AA%23ABA
The resulting price is $550 + tax (free shipping).

For that price, I see she gets a good laptop, but I chatted for half an hour with the HP
sales chat people and they couldn't confirm if this 802.11 n/ac laptop has both
2.4GHz and 5GHz or if it only has one of those two frequencies.

HP chat sent me this URL but it just confirms that both "ac" and "n" don't have to be dual
band; either one can be a single band. Also, it confirmed the 1x1 or 2x2 or 4x4 just means
the number of dedicated data transmit and data receive antennas, which says absolutely
nothing about the frequency.
http://www.intel.com/content/dam/www...or-dummies.pdf

My question is ...
How can we tell from the HP WiFi card spec whether the NIC is 2.4GHz or 5GHz, or both?