The daily exchange rate of one dollar in euros during the first three months of 2007 can

Question:

The daily of one dollar in euros during the first three months of 2007 can be inferred to have the following distribution.
X P(x)
0.73 ... 0.05
0.74 ... 0.10
0.75 ... 0.25
0.76 ... 0.40
0.77 ... 0.15
0.78 ... 0.05
a. Show that P(x) is a probability distribution.
b. What is the probability that the on a given day during this period will be at least 0.75?
c. What is the probability that the on a given day during this period will be less than 0.77?
d. If daily exchange rates are independent of one another, what is the probability that for two days in a row the will be above 0.75?
Exchange Rate
The value of one currency for the purpose of conversion to another. Exchange Rate means on any day, for purposes of determining the Dollar Equivalent of any currency other than Dollars, the rate at which such currency may be exchanged into Dollars...