Evaluate the number of license plate from the given data.
a. How many license plates can a state have if each license plate has 2 letters followed by 4 digits, if the first digit cannot be zero?
b.
1. A class consists of 15 students. The instructor wants to pick a group of 4 to work on a special project.
2. How many different groups of 4 can he choose? If the class consists of 10 girls and 5 boys, how many different groups of 4 are made up of 2 boys and 2 girls?