Verify that the following function is a probability mass function, and determine the requested probabilities. [give exact answers in form of fraction.]

f left-parenthesis x right-parenthesis equals left-parenthesis 4divided by 5right-parenthesis left-parenthesis 1 divided by 5right-parenthesis superscript x baseline , x equals number 0 , 1 , 2 , . .

(a) upper p left-parenthesis upper x equals 2 right-parenthesis equals (b) upper p left-parenthesis upper x less-than-or-equal-to 2 right-parenthesis equals
(c) upper p left-parenthesis upper x greater-than 2 right-parenthesis equals (d) upper p left-parenthesis upper x greater-than-or-equal-to 1 right-parenthesis equals