Meta Software Engineer interview questions

The Facebook company store sells stickers that say the word “facebook” on them. We just got a new shipment in, and we have way more than we know what to do with. We came up with a plan: we can make posters by cutting and pasting the letters in the word "facebook" to make other words. Given a particular source string representing a word on a sticker, write a function that tells me how many stickers of that string I need in order to make a given target string. Your function should take in both a source string and target string, and return the number of stickers.