How can I solve the problem by solver (with attachment)

Hi all,

I attached an excel file in which I wanna achieve a result to get the closest average price for each customer.

Details:
There are total quantity of 300 shares for the same stock ordered eqaully by 3 customers (A,B,C).
The acutal executed orders are in the lower part of worksheet1. 300 shares were bought in total of 6 transactions.
I have to allocate the executed orders to the 3 customers and ideally the average purchase prices for them are as closer as possible. One constraint is that the allocation of shares must be in a mulitple of 50. For example, to customer A, the average price must be derived from any two in combination ( $1, $1.1, $0.95, $1.2, $1.15 and $1) though the weighted average price is $1.0666 for the total 300 exexcuted orders.
I wanna achieve my goal by using Solver. Can anyone help? Thanks in advance