Urgent help needed please !!

In a given sample student size of 90, 2 persons are underweight, 61 healthy weight, 25 overweight and 2 obese. If we select a randomly a student from the university where the sample was drawn, what is the probability that the student would be:

a) Underweight
b) Healthy Weight
c) Overweight

Also, how can I show the p-value as the area under normal curve for each of the weight categories?
If I am not mistaken, answers are quite simple.

a) 2/90
b) 61/90
c) 25/90 (or 29/90, if you count obese students as special 'case' of overweight as well)