Read the following premise and answer if the hypothesis is true.
Thanks to the thirty Heads who responded to my question about maternity leave. Clearly, the amount of maternity leave offered to teachers at international schools varies greatly from school to school.
Hypothesis: Twenty plus ten heads heads did not respond to the question. Is the answer "Yes", "No", or "It's impossible to say"? Respond with only the answer and no additional text.
No
It's impossible to say. The hypothesis does not provide enough information to determine the exact number of heads who did not respond.