Please Help With Questions #2 and #3

The probability that a tutor will see 0, 1, 2, 3, or 4 students is given below determine the probability distribution's missing value.

Margie is practicing for an upcoming tennis tournament. her first serve is good 20 out of 30 times on average. margie wants to know the estimated probability that her first serve will be good at least four of the next six times she serves. how could she design a simulation for this scenario?

Which has the greater energy, light of wavelength 519 nm or light with a frequency of 5.42 x 10^8 sec^-1?