1C-Bitrix "Small Business"Working with a shopping cart

In the editorial office "Small business" there is no support for sets of goods. There's a draught beer in the store. There are trade offers: One name is presented both in a liter and one and a half liters. That is, when pressing "+" + "quot; 1 liter is added. If you choose a liter icon, and 1.5 liters. If you've got a one-and-a-half.

Task: when pressing "+" should be added empty bottle (with a picture, with a price, completely the product, in a word) for a liter of its own, for one and a half, respectively.
The number of liters should correspond to the bottles in the basket.