Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:

Convert text to sql: How many students have had at least one "B" grade? | student : stuid , lname , fname , age , sex , major , advisor , city_code | faculty : facid , lname , fname , rank , sex , phone , room , building | department : dno , division , dname , room , building , dphone | member_of : facid , dno , appt_type | course : cid , cname , credits , instructor , days , hours , dno | minor_in : stuid , dno | enrolled_in : stuid , cid , grade | gradeconversion : lettergrade , gradepoint | member_of.dno = department.dno | member_of.facid = faculty.facid | course.dno = department.dno | course.instructor = faculty.facid | minor_in.dno = department.dno | minor_in.stuid = student.stuid | enrolled_in.grade = gradeconversion.lettergrade | enrolled_in.cid = course.cid | enrolled_in.stuid = student.stuid | 

### Response:

select count ( distinct _ ) from _ where _ | select count ( distinct stuid ) from enrolled_in where grade = 'B'