Determine whether the following value is a continuous random variable, discrete random variable, or not a random variable.
a. the number of light bulbs that burn out in the next year in a room with 15 bulbs
b. the hair color of adults in the united states
c. the exact time it takes to evaluate 67 plus 29
d. the number of free dash throw attempts before the first shot is missed
e. the time required to upload a file to the internet
f. the number of statistics students now doing their homework