Trying to calculate average of percentile range in a normal distribution

[Brad Merchant]

Hello,

I'm trying to generate a data set for future sales performance for my sales team, and calculate the average sales conversion rates for 4 different percentile ranges:
80%-100%
60%-80%
20%-60%
0%-20%

Assuming a mean conversion rate of .36, a population of 82, and following a normal distribution, how can I calculate what the average score would be for all scores in each of the above ranges? I was able to use this online calculator to determine the conversion rate at each percentile mark: https://www.wolframalpha.com/widgets/view.jsp?id=67817f2e01eecd366e6d73ac7a71bcd1, but I'm looking to find the average of scores within each range.

Thanks in advance for any help!