Pressed by lawmakers for details on the proposed Wisconsin Covenant, Gov. Jim Doyle’s administration has slapped a price tag on it: $139 million over six years. The estimate didn’t quiet critics, who want more details about the workings of a program in which an eighth-grader pledges to maintain at least a B average in high school and meet other benchmarks in exchange for a guarantee of a seat in a Wisconsin college and, if eligible, a financial aid package.