Vince asks baseball players how many years they have played baseball. He separates the responses by school grade and records them in the table below. What is the joint frequency of ninth graders who have played for 6 years?
Grade
4
Years playing baseball
5
6
7
0
8
6
8
10
6
7
4
8
7
14
8th grade
9th grade
10th grade
Ilth grade
12th grade
11
9
6
9
10
7
5
12
6
11
6
1
9
2.
6