A random sample of 70 printers discovered that 20 of them were being used in small businesses. Find the 99% limit for the population proportion of printers that are used in small businesses.
a) 0.021 < p < 0.551
b) 0.146 < p < 0.425
c) 0.160 < p < 0.412
d) 0.239 < p < 0.332