[Grammar] was the sudden breakdown of

[Oceanlike]

In a synthesis exercise, my answer to the following question was:

Q: The washing machine suddenly broke down. Mother was frustrated.

My answers: What frustrated Mother was the sudden breakdown/breaking down of the washing machine.
(I have to start with 'What frustrated Mother......)

Can both 'breakdown' and 'breaking down' be grammatically correct? I only know that they sound right.

Thank you! :-D

 

[emsr2d2]

They're both OK in BrE.

There are other possibilities, such as "What frustrated Mother was that the washing machine had suddenly broken down".