How much caffeine is in Stop&Shop brand diet cola?

I have been needing caffeine to keep my mood stable lately and I know that diet coke has 46mg per 12 oz., which is a good amount more than regular coke. I have been looking online but I can't find the amount in the S&S brand and it's not on the bottle and I dont like paying the extra dollar just for the brand name. Does anyone know if it has more or less or the same? And how much?