A startup business school cafe tracks the number of premium…
A startup business school cafe tracks the number of premium coffees a randomly chosen customer buys in one visit. The random variable XXX denotes this number. Based on past data, the probability mass function of X is: P(X=x)={0.1,x=0(no premium coffee),0.2,x=1(one premium coffee),0.3,x=2(two premium coffees),0.4,x=3(three premium coffees),0,otherwise.P(X=x) = \begin{cases} 0.1, & x=0 \quad (\text{no premium coffee}), \\ 0.2, & x=1 \quad (\text{one premium coffee}), \\ 0.3, & x=2 \quad (\text{two premium coffees}), \\ 0.4, & x=3 \quad (\text{three premium coffees}), \\ 0, & \text{otherwise}. \end{cases}