physics professor wants to know what percent of physics majors will spend the next several years doing post-graduate research. He has the following probability distribution.

p p(x)

1 .45

2 .25

3 .10

4 .10

5 .05

6 .05

Find the probability that a physics major will do post-graduate research for at most three years. (Enter an exact number as an integer, fraction, or decimal.)

P(x3) =