The following two-way table shows the places where high school students have volunteered in the past month. the table will be converted into a relative frequency table. which value is the joint relative frequency of the number of 10th grade students who volunteered at the animal shelter?

9th grade 10th grade 11th grade 12th grade total
animal shelter 6 8 4 10 28
hospital 12 17 13 19 61
library 5 6 4 7 22
boys and girls club 9 14 15 11 49
total 32 45 36 47 160