In Assembly Langauge for x86 (MASM)

How would you add two WORD variables with two DWORD variables taken from user input? For example, user enters 10 for variable 1 (WORD), 20 for variable 2 (WORD), 30 for variable 3 (DWORD), and 40 for variable 4 (DWORD) for a sum of 100? Explain how to add the two 16bit register values with the two 32bit register values.