Average calculation per persoon

Hiii,

I have 2074 customers with orders and amount, what I need, I want to know average order per person with average amount.

for example:

John 3 orders $10
Mary 5 orders $5
Sally 10 orders $10

Now I need the total average. So

(3 + 5 + 10)/3 = 6 orders

($10 + $5 + $10)/ 3 = $8.3