Observe.AI Senior Software Engineer interview questions

A school teacher has got n different problem ideas and there is a total m number of tags. Each problem has some tags associated with it represented by a 2d array tags where tagslilli] = 1 if problem i contains jth tag otherwise tagsfi][i] = 0. Also, each problem has a cost that is to be paid to prepare which is represented by an array cost of length n. It is guaranteed that for each m tags there is at least one problem that covers it. The goal is to choose some problems out of these n problems such that all the m tags are covered with minimum cost.