How many of the following $X$'s are continuous Random Variables?
i. $X=$ The number of people enter a store between 1pm and 2pm.
ii. $X=$ The price of an iPhone 6 being sold at Best Buy on 07/01/2016.
iii. $X=$ Time.
iv. $X$ is a random variable with probability density function $f(x)= 2x$ for $0< x< 1$.
v. $X$ is the variance of a sample of size 50 that is to be collected from some infinitely-large population.
vi. $X$ is the investment return of a portfolio over a 1-month period.