<s>[INST] For a particular birthday party, Tom orders a combination of plain and chocolate cake cupcakes to provide at least one cupcake for each of his guests. The plain cupcakes cost \$2.50 each and the chocolate cupcakes cost \$3.25 each. If Tom would like the total expenditure on cupcakes to be between \$120 and \$150, what is the ratio of plain cupcakes to chocolate cupcakes?[/INST]