The expected value formulas for discrete and continuous variables follow the same basic principle:

Summation of [ x * p(x) ]

Your answer is essentially correct, but you may want to:

1.make the midpoint of each category as 34.5, 44.5, 54.5, 64.5

- for example, the midpoint of 30,31,32,33,34,35,36,37,38,39 is 34.5

2.and extend the probabilities by one decimal place.

You'll get an answer of 44.85, which is a bit more precise.