Answer: $1,395
Explanation:
Not all the above can be counted as Revenue so first I will differentiate them to make calculating revenue easier. 
a) Received $960 cash for services provided to a customer during July.
- This is Revenue as it was received in payment of work done. 
b) Received $3,200 cash investment from K. Peterson, the owner of the business.
- This is an Investment into the business and so is NOT Revenue. 
 c) Received $810 from a customer in partial payment of his account receivable which arose from sales in June. 
- This is NOT Revenue but is the settling of an Accounts Receivables. 
d) Provided services to a customer on credit, $435. 
- This is Revenue as it is rendered for services provided. 
e) Borrowed $6,600 from the bank by signing a promissory note. 
- This is NOT Revenue as it was long term borrowing. 
f) Received $1,310 cash from a customer for services to be rendered next year.
- This is NOT Revenue as it is Prepaid Revenue. 
Adding up those considered Revenue we have,
= 960 + 435
= $1,395
$1,395 is the amount of Revenue in July.