Handling many to many relationships (corrections made)

(There were issues with the design in my original post. Those have been corrected. I have let the errors stay and have highlighted where I have made corrections so that you can understand better)

Consider this situation.

2 new guys Ravi and Raj go to our bank and open new savings accounts 101 and 102. And Ravi deposits 100 and Raj deposits 144. This can be represented by the following.

CLICK ON THE IMAGES BELOW TO SEE A LARGER PICTURE

Now suddenly, Ramu and Ramya come to the bank and open a joint account 103. And they deposit 1000. How will you represent this? What will you enter for CUST_KEY ? Will you enter 3 or 4? It was the same transaction of Rs 1000. But which customer to indicate? What will you fill in the red ? position below?

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