Identify the type of sample and whether it is a biased or unbiased sampling method.

To represent all employees at the company, the boss surveys all of the workers on the first shift.

Every 15th person who enters the workplace is surveyed.

A computer program takes the names of all the students in the school, mixes them up, and randomly selects 20 students.

A principal surveys the eight girls on the volleyball team to represent all of the girls in the school.

The customers who willingly participated in the survey use the web link printed on all the receipts.

PLS ANWSER QUICK!!!!!!!!!!!!!!!!!!