At a time when demand for ready-to-eat cereal was stagnant, a spokesperson for the cereal maker Kellogg's was quoted as saying, "..... for the past several years, our individual company growth has come out of the other fellow's hide." Suppose that when Kellogg's and its largest rival advertise, each company earns $1 billion in profits. When neither company advertises, each company earns profits of $12 billion.

If one company advertises and the other does not, the company that advertises earns $46 billion and the company that does not advertise earns $2 billion. For what range of interest rates could these firms use to trigger strategies to support the collusive level of advertising?

i < __________ percent