At least one black can be chosen in two ways from each box:
Now, probability of choosing at least one black ball from first box 

= 1/2 × [ (2C1× 2C1)/4C2 + 2C2/ 4C2 ]= 5/12

Probability of choosing at least one black ball from 2nd box
= 1/2 × [(4C1×12C1)/16C2 + 4C2/ 16C2] = 9/40

Final probability

= 5/12 + 9/40 = (50 + 27)/120 = 77/120

A Group of birds or a flock flying together in hundreds or even in thousands is called Murmuration.

In accounting, the Three-way Match refers to a procedure used when processing an invoice received from a vendor or supplier. The three-way match is an important step in safeguarding an organization's assets. The purpose of the three-way match is to avoid paying incorrect and perhaps fraudulent invoices.

Here Three-way refers to the three documents involved :

* Vendor's invoice which was received and will become part of an organization's accounts        payable if approved.

* Purchase order that was prepared by the organization.

* Receiving report that was prepared by the organization.

And Match refers to the comparison of the quantities, price per unit, terms, etc. appearing on the vendor's invoice to the information on the purchase order and to the quantities actually received.

After the vendor's invoice has been validated by the three-way match, it can be further processed for payment.