Probability question

#1
Hi All
Need your help to solve below question of probability.
Question: There are 300 students in an online MBA program for working professionals, for whom the attendance in online classes is 70%, i.e. on an average, 210 students are present in an online session. Fifty new students are admitted in this batch.
a) What is the probability of attendance being at least 70% among the new students, thus ensuring the overall attendance does not fall below 70%?
b) The Program Dean thinks that this probability will increase, if the new batch size is 40 instead of 50 students. Is he right in assuming so?
 

Dason

Ambassador to the humans
#2
Are we to make the assumption that the true probability that each of the 50 new students will attend or not ends up being 70%?