During fiscal 1995, Ashland Exploration drilled 7 wells in the United States and 3 in Nigeria. One of the wells in Nigeria was productive and 2 of the wells in the United States were productive. The remaining wells were dry. For a well selected at random from those drilled during fiscal 1995, determine the following probabilities.
a. P(drilled in the United States)
b. P(drilled in the United States or dry)
c. P(dry drilled in Nigeria)