Hypothetical Mergers question horizontal, question, because, another, company

LorrinCFA

Family company owns three subsidiaries: Clothing, Food, and Drug.
Food purchases another Food company in the same part of the supply chain.
Is the merger a) horizontal (because Food purchases Food) or b) conglomerate (because Food is a subdivision and a part of Family, which is a conglomerate, so you have a conglomerate merging with another firm)?