eumhic
I don’t quite agree with the solution. Surely the absolute minimum number of customers would be 2. The question never states that a customer can only purchase 1 pizza only 1 type of pizza i.e. margarita or pepperoni. Thus, you could have 1 customer by all the margaritas and another buy all the pepperoni.
You should read the question more carefully. It explicitly states that no customer purchased more than one pizza of a particular type, which means a customer can buy at most one Margarita and one Pepperoni. Therefore, a single customer cannot buy all 70 Margaritas or all 100 Pepperonis, and having only 2 customers is not possible.
By the way, this doubt has already been addressed in the thread, so please read the topic carefully as well.