The Roth IRA's principal difference from most other tax advantaged retirement plans is that, rather than granting a tax break for money placed into the plan, the tax break is granted on the money withdrawn from the plan during retirement.
DK is a UK (and maybe Australia - but not sure on that) weight of yarn ... Double knit or DK weight is heavier than sportweight and lighter than worsted weight. Here are the guage ranges for a 4 st st swatch. # of sts is the number of stitches in 4 inches.
TammyK (a regular here) DK is slightly lighter weight than worsted. Here in the U.S. it is classified as a #3 weight class while worsted is a #4 weight class. (Most U.S. yarns have the weight class on the label, but not all of them.) I'm sure you could use DK on a knitting machine that works for worsted, but I don't know what gauge you would get.