Final answer:
The source port number in the given UDP header dump is 0045.
Step-by-step explanation:
The source port number can be found in the UDP header. In the hexadecimal dump provided (0045DF0000580000a), the source port number is the first 4 characters, which are 0045 in this case. The source port number is a 16-bit value that identifies the sending process or application on the sender's device.