A social organization of 32 members sold college sweatshirts as a fundraiser. The results of their sale are shown below.
No. of sweatshirts No. of students
0 ..............2
1–5 .............13
6–10 ............8
11–15 .............4
16–20 .............4
20+.............1
Choose one student at random. Find the probability that the student sold
a. More than 10 sweatshirts
b. At least one sweatshirt
c. 1–5 or more than 15 sweatshirts