In a recent study found that 80% of Covid-19 patients did not have adequate levels of vitamin D in their blood. In a random sample of 10 patients, what is the probability:

1. At least five did not have adequate level of vitamin D in their blood.
2. At most 4 did not have adequate levels of vitamin D.
3. More than 7 did not have adequate levels of vitamin D.
4. For x=0 to 10, determine the probabilities of the events to find the variance, and standard deviation for the Covid-19 patients did not have adequate levels of vitamin D in their blood?