19. The number of contaminating particles on a silicon wafer prior to a certain rinsing process was determined for each wafer in a sample of size 100, resulting in the following frequencies:

Number of particles 0 1 2 3 4 5 6 7 Frequency 1 2 3 12 11 15 18 10 Number of particles 8 9 10 11 12 13 14 Frequency 12 4 5 3 1 2 1

a. What proportion of the sampled wafers had at least one particle? At least five particles?

b. What proportion of the sampled wafers had between five and ten particles, inclusive? Strictly between five and ten particles?

c. Draw a histogram using relative frequency on the vertical axis. How would you describe the shape of the histogram?