HP India — printer cartridge colour 802 small

Address:

560016

I have purchased a cartridge 802 colour small. The price of the cartridge which is imported oct 16 is shown as rs. 906/- (Inclusive of all taxes). The price now is shown as rs. 1288/ — (Inclusive of all taxes), revised mrp with gst. I would like to know the following details:
1. What is the gst rates on cartridges.
2. The price of rs. 906/- is already inclusive of the customs duty and the vat payable at that point of time, i. E., inclusive of the vat payable by the dealer also, so why is there an increase of rs.382/- on mrp which is much higher than the maximum gst of 28%, even if we take the gst to be on mrp, which is not the case.
Request that i may kindly be replied to within the shortest period.